The R5 camera is a good starting point -- it is the first true unicorn camera, possessing both a high megapixel count (45MP) and high frame rate (20fps with electronic shutter, 12-bit files vs 14-bit mechanical).  When the R5 was announced, my kit included the 5D IV and the 1DX II, i.e. a general purpose high(er) MP body (30MP at 7fps) and a high frame rate sports/wildlife body (20MP at 14fps).

Based on specs, the R5 could replace either -- or both.  It checked all the boxes in the decision table above, so the only decision was which camera to trade in.  Given its advantages in the field it replaced the 1DX II, despite its less robust build quality.  This defers the purchase of a pro-level sports and wildlife body until a suitable pro model is introduced, see next below.  When that happens, the R5 will assume the role of general purpose camera -- the R5 being superior at that application as well.  In the interim, the 5D IV continues to be the general purpose camera.

The professional quality R3 is a higly-regarded body, an example of what Canon can do when they put their best effort forward.  With one exception, it cures all the shortcomings of the R5 and adds a few wrinkles of its own.  Most notable is eye-controlled focus point selection, something that worked adequately well on the EOS 3 film camera.

Another bonus is that it achieves 30fps electronic shutter with full 14-bit output files.  This was a significant shortcoming with the R5, which dropped to 12-bit files in electronic shutter mode.  But, and it is a big one for me based on my R5 experience, the camera only delivers 24MP.  The R5's 45MP sensor enables deep cropping, and for my uses this has been extremely valuable.  Thus, while it checked almost every decision box it failed the acceptable specs test and has been passed over.  Also, there appears to be a better alternative in the offing, the mysterious R1 professional body, the specs for which are yet to be revealed.

If an R1 ever appears, and if it carries forward the good features and specs of the R3, it will be carefully considered as the eventual replacement for the EOS 1DX II body.  However, there are some some critical no-go specs that must be met.  First, the 45 MP count of the R5 must be matched or exceeded.  Less would cause it to be passed by.  Also, price must be acceptable, i.e. in the range of the Canon R3, the Nikon Z9 and the Sony A1.  If these attributes are not met, then it will be time to consider another R5, or perhaps an R5 Mk II follow-on, if and when such is released.

The Canon EF11-24mm f4L lens is an exemplary ultra-wide zoom, acceptably sharp throughout its range.  Distortion in the corners at the widest zoom settings can be obnoxious, but this is the inevitable consequence of a rectilinear design.  In any case, said distortion can be minimized by keeping the camera level to the horizon when possible.  Or, by applying keystone and cropping objectionable parts.

This focal length range isn't one I use frequently.  Therefore, it would appear to fail the frequency of use criterion.  However, there are times when the focal length is highly useful, especially for landscape and architecture photography.  For walk around situations, weight becomes a dominant factor.  The down side of the EF11-24mm zoom is that it weighs 2.6lb.  Combined with a gripped EOS 5D IV one is dragging around a 5.5lb lump -- a bit more than I care for during an extended walk.

The RF14-35mm f4L weighs only 1.2 lb, shaving 1.4lb from the total, a more palatable all day carry.  The tradeoff is loss of 3mm on the critical wide end, somewhat compensated by 11mm more on the long end.  The fact that the lens requires heavy distortion correction in post processing is a bit of a put-off.  But, in the end output image quality and weight are the final arbiters, and there it passes muster.

Oddly enough, I couldn't bring myself to trade in the 11-24mm, instead keeping it on hand for ultra wide situations where carrying weight is less of an issue.

The original Canon EF 24-104mm f4L lens is one of my most used optics, along with my long telephotos.  The thought of moving to the latest mount and technology is appealing.  However, a Canon white paper discussing the RF equivalent in comparison to an earlier EF version was not encouraging.  it detailed a mixed performance across the focal range, better at some settings, worse at others.

Ever hopeful, I rented an RF sample and compared it directly with my now ancient and much used EF version.  The results were disappointing.  In some ways, my original was better than the new RF lens.  This could, of course, be attributable to sample variation, an affliction for which this focal range is notorious.  But, based on Canon's own admission combined with my personal comparison testing the sad conclusion was that this new RF lens failed the very first decision test -- it did not provide a "significant upgrade to current gear."

On the other hand, there is a Canon patent for another midrange f4 zoom, an optic that would feature an expanded zoom range on the long end, 24-150mm.  Unless image quality is seriously deficient, it would be an instant purchase.  The expanded focal length on the telephoto end is well worth having.

My EF70-200 f2.8L II gets little use, mostly family portraiture and the occasional general purpose outing.  Since it doesn't pass the "significant upgrade"  test or the "frequency of use" criterion it must remain a nice to have rather than a compelling upgrade item for the present.

The RF100-500mm is reputed to be one of the finest lenses Canon has made.  When I was attending professional tennis tournaments the 100-400mm zoom was my lens of choice.  But, that application is no longer relevant.  If this zoom range was used more frequently the RF100-500 would be an easy upgrade.  It is somewhat like having a 100-400mm optic with a built in extender.  However, for present uses the current EF version sees little action.  Thus, it is difficult to justify the expense.  And yet, despite this entirely rational logic the lens is awfully tempting. . .

For historical architecture -- a frequently photographed subject and personal favorite -- as well as landscapes to a lesser extent, the Canon tilt-shifts are a cut above the competition, not only in quality and features but also in number of choices.  An RF14mm tilt-shift would be a useful addition -- if price is palatable and performance is excellent.  Time will tell.

For years, my go-to long lens setup has been a tripod and gimbal mounted 600mm f4 lens, often with a 2X extender attached, yielding a focal length of 1200mm.  Even then, cropping may occasionally be needed.  The R5 has greatly aided in this latter requirement.

However, chasing flighty shorebirds and other jittery subjects with a tripod setup can be exhausting, especially when crouching to stay low but also moving as the subject moves.  Recent experience convinced me that for my trips the best results are obtained with a handheld telephoto setup.  For the present, that consists of an adapted EF400mm f4 DO II mounted on an R5, and often with a 1.4X or 2X extender attached.  This rig, minus the extenders also serves as a birds-in-flight combo as well as a deer photography rig in the mountains.  This setup comes in at eight pounds, at the limit of what I can personally carry and handhold.

But, this lens and extender pairing maxes out at 800mm.  Longer would be better, ideally in the 1000mm to 1200mm range.  Canon professional quality DO releases have gotten rather scarce in recent years.  But, a lens built to the specs of this 500mm f4.5 DO lens patent would merit consideration if the design ever becomes reality.  Although it would not go beyond 1000mm it still would be an improvement over the current 400mm DO with extender.  Time will tell what is actually delivered, with what optical performance, and at what price.

Another patent has emerged that might work, an RF500mm f4L.  A quick comparison of the weight reduction of EF600mm f4Ls hints that such a lens could come in at about five pounds, close to that of the current EF400mm f4 DO.  Optically, this would be an even better solution than the 500mm 4.5 DO introduced above.

The above goal of getting as much quality handholding focal length as possible in a lens/camera combination weighing no more than eight pounds leads to consideration of the Nikon Z800mm f6.3 PF combination.  Careful comparison of the weight of the lens combined with a Nikon Z9 camera and battery reveal that it weighs almost exactly the same as my Canon EF400mm f4L DO II setup, i.e. with added 2X extender and control ring adapter, all fitted onto a gripped R5 with two batteries.  This pair would give 1120mm with a 1.4X teleconverter and a whopping 1600mm with a 2X.  Talk about up close and personal!  On specs, it is a much better choice than not only the current setup but the patented lens formula above -- which may never be produced anyway.

Even ignoring the fact that demand for this exceptional Nikon lens far outstrips supply, I am still undecided on what to do.  One of the key barriers is assessing whether the benefits from this Nikon addition is greater than the personal aggrevation of learning and using a second system.  If this lens were available on a Canon RF mount camera it would be on order already.  But it isn't.  So, we continue to read Z9 manuals and try to imagine coexisting with something substantially different than our Canon gear, a system that has become second nature from long use and familiarity.  Not to mention that I simply like Canon's ergonomics, buttonology and menus.

The above products are the most likely to be purchased in the not-too-distant future.  However, since our current EF lineup pretty much covers personal needs none requires immediate attention.  Perhaps it is a tribute to Canon's transition to mirrorless that EF mount lenses can be so seamlessly adapted to the R line of cameras.  And to the excellence of the R5 as a game changing do-everything camera.  In the interim, we'll keep an eye on new announcements and evaluate each as it happens.

Releases that would pique immediate interest include the rumored R1 body, a high quality midrange zoom such as the patented 24-150mm f4L optic and a hand holdable long telephoto capable of reaching 1000mm or more with extenders. The RF100-500mm might join that group on quality and flexibility alone, essentially a 100-400mm with built in extender. This lens is, perhaps, the best example of the "I want it now!" fixation!

For the near future, MILCs and DSLRs will be used side-by-side. In the long run, an R1 or R5 II purchase would lead to an all-MILC camera body setup. At that point, it would make sense to move to the RF24-105 f4 or successor, RF70-200 f2.8 and RF100-500. Current EF tilt-shifts would almost certainly remain as there is little down side to using them with adapters. That would leave the EF telephotos as the last holdouts, with upgrades dependent on what might be released in the future.

Meanwhile, the tables below show how each near-term decision was arrived at.