That sounds like a likely specification for the rumoured upcoming replacement for the R, and I think it will be cheaper than you suggest.Am I the only one that would just like an R5 that's 30mp, 4k oversampled, no 8k, No overheating and about $2500. - $3500?
Obviously it woundnt be called an R5 but you get the idea
I think it will be based on the R6 body though, not the R5, but that's no bad thing.
My guess is 33MP, IBIS, and possibly a different menu and EF interface for stills and video.