Many video teams rely on the 5D series and probably will continue to even if they don’t hack it. But maybe they’ll also include some sort of RAW video recording ability.
For us photographers though, I’m sure what most are looking for is a combination of higher megapixels for prints and cropping (especially for the wedding crowd) in addition to better high ISO output. As it is, the 5Ds has surprisingly good high ISO image quality and it’s bound to come to the next 5D camera. Additionally, faster FPS, more AF points, and WiFi transmission being put into the camera will make a lot of sense.
Many DSLR users also wear glasses–and if some sort of extra adjustments to the diopter could be made, it would make a lot of sense. Just sayin’! If anything should have it, it would be the Canon 5D Mk IV.