This sounds almost too good to be true. The last Canon body I purchased was a 5D3 in 2012, so I'm itching for something new, especially as a mirrorless hybrid shooter.
I'm going to guess this camera comes in at a minimum of $4,500. The 5D3 and 5D4 both came in at $3,500, so an extra $1,000 isn't too unreasonable for the specs and tech they're cramming into a mirrorless body. Of course, my mind will be blown if the release the R5 at the standard $3,500 or less.
My only concern is on the video side. I haven't done any work using HEVC/H.265. Correct me if I'm wrong, but the only camera in recent memory I can recall using the codec was the Samsung NX1. How does this codec compare compared to MotionJPEG of the 5D4? Will it require transcoding to ProRes or DnX or the use of proxies for efficient video editing? Can most computers handle it well?