The roles have reversed.
Back at the Tokyo Olympics (2021 due to COVID delays), Canon had a pro camera ready (R3) and Nikon had a prototype (Z9). For the Paris Olympics (2024, begins end of July), Nikon now has a top pro camera that's been reiterated five times (Z9), and Canon will now have a prototype (R1).
Today Canon posted a Development Announcement for the R1, with the only substantive information being that there is a newly developed adjunct image processor (Digic Accelerator) and new CMOS sensor. Strong hints at changes to the focus system and what it can recognize were also given.
A photo of the front of the new R1 allows comparison with the R3: the R1 is a little bigger and continues Canon's swoopy design ethos.
Update: some retailers around the world briefly posted, then withdrew, some additional information:
- 30mp stacked image sensor
- Fast readout speed allows 1/1250s flash sync
- Frame rates from 40 fps (low compression raw) to 60 fps (higher compression raw), with a maximum of 240 fps (probably JPEG)
- Increased dynamic range over R3
It's unclear if this information is accurate, however it was interesting that multiple stores seemed to have posted additional information and then withdrew it.