I am not suggesting the photographers care, I am saying Canon would care.
Those use cases don’t seem to require an extremely rugged body with an integrated grip.
Consider this: for many years Canon carried both the 1D line (faster, lower MP, sports/PJ) and the 1Ds line (slower, high MP, wedding/commercial). When they ‘merged’ those lines, the resulting 1D X and its successors looked essentially like the 1D.
A ‘cycle’ after that merge, Canon increased the MP of the 5-series to the highest FF MP count (50 MP in the 5Ds/R) in a Canon FF camera to date – the ‘crown’ first held by the 1Ds series. 1Ds -> 5Ds. The torch was passed.
That seems like good evidence Canon feels the high MP needs are best met by a 5-series body. Thus we also have the R5 at 45 MP. I expect the R5s will be along as some point with a 60-80 MP sensor and modest fps. Then the R1 at modest MP.
What's different now compared with the recent DSLR
I am not suggesting the photographers care, I am saying Canon would care.
Those use cases don’t seem to require an extremely rugged body with an integrated grip.
Consider this: for many years Canon carried both the 1D line (faster, lower MP, sports/PJ) and the 1Ds line (slower, high MP, wedding/commercial). When they ‘merged’ those lines, the resulting 1D X and its successors looked essentially like the 1D.
A ‘cycle’ after that merge, Canon increased the MP of the 5-series to the highest FF MP count (50 MP in the 5Ds/R) in a Canon FF camera to date – the ‘crown’ first held by the 1Ds series. 1Ds -> 5Ds. The torch was passed.
That seems like good evidence Canon feels the high MP needs are best met by a 5-series body. Thus we also have the R5 at 45 MP. I expect the R5s will be along as some point with a 60-80 MP sensor and modest fps. Then the R1 at modest MP.
In terms of sports photography, I think Canon cares more that there are big white lenses at events than which specific camera models are being used as long as they are pro-level ($$$) models. The R3, only $500 cheaper than the 1DX3, will provide Canon with a good market share and significant profits.
In terms of the overall camera line, Canon has already shown that they are going in a different direction than their recent DSLR history with their first ever pro-body that is not a "1" series camera. Some say that it is an interim camera until the 2024 Olympics. I disagree for the following reasons:
1. Too high a premium for an upgrade. Imagine that you are a sports photographer now and looking for a mirrorless camera. So you go out and buy an R3 for $6K. In three years you are going to shoot at the Olympics and Canon comes out with a low MP R1 (the replacement for the R3) and they want $8K for it. True it will likely have global shutter and better autofocus. But $2K better? If I'm that guy, I'm scrambling to buy another R3 instead. It's tough to pay that much more for a camera that will be used for the same purpose.
2. Profits. A high MP R1 with global shutter, 16 bit files, and lower FPS than the R3 would be attractive to a wide variety of professionals and enthusiasts (wildlife, macro, landscape, commercial, architecture, etc). Canon could justify the $8K price based on pro-body, high MP, plus these other improvements over an R3. However, if they leave the high MP model to the 5 series, they will only be able to charge maybe $4,500 for it. I believe they would be able to sell many high MP R1s at $8K as there seems to be a market for premium high MP cameras such as the Fuji GFX 100s. Canon would want a piece of this market. There would still be room for a ultra high MP R5, but it likely wouldn't have a BSI sensor, global shutter, 16 bit file, etc and therefore priced accordingly.
3. Size reduction will make the R1 more attractive for non sports photographers. The R3 body is significantly smaller and lighter (I assume, no weight data yet provided) than the 1DX3. This is important because a future R1 will I believe likely also have a similar form factor, and therefore the weight penalty of going to a 1 series vs 5 series camera is much reduced compared to the DSLR era. This will make the R1 much more attractive to commercial and wealthy enthusiast photographers that had been using a 5 series camera due to the excessive size of the existing 1 series camera.
So these are the reasons why I believe the R1 will be a high MP camera instead of a replacement for the R3. But only time will tell.