According to latest rumors on CR, a pro/high-end mirrorless camera with both RF mount and EF mount is in the works. This means you will be able to mount both RF lenses and EF lenses without the use of an mount adapter. This would be a great news for Canon shooters.
This camera was being developed for the “EOS-1 style EOS R camera”, which would make a lot of sense. The size for this EOS R Pro mirrorless camera is not all that important.