I continue to believe that the R3 will be for the sportshooter, and 100+ MP R1 for studio, with global shutter and perhaps pixel binning option to allow for occasional medium to high frame rate shooting.I think Canon will struggle to create a distinction between the R3 and R1.
I can’t see the R1 being bigger in size (there would be no practical reason to be bigger - battery size would be likely to be the same). Weather sealing would be the same.
They’d be down to say focusing ability , it would be very poor of Canon to only implement a better focusing system on an R1. It would be at best a software enhancement.
They could distinguish based in MP. 45 v 100 MP. I think there would likely be a trade off here. The 45MP might be superior at high ISO.
They could distinguish based on FPS but that is a real diminishing return. There’s very limited uses where 30 FPS is more useful than 20 FPS
I think they will find it hard to make an R1 a compelling prospect with an R3 in existence. It’s existence and high price might improve the sales of the R3 once both exist.
(It sort of reminds me when Olympus brought out the M1X and I thought what was the point with the OMD EM 1 Mark III in existence - bigger battery and a few software tricks were the main improvements)
The R3 will simply be too good for an R1 to outclass it for sports and wildlife, and therefore the R1 needs to serve a whole different purpose.