Lots of good ideas posted already.
I'd like to see them put an electronic aperture control ring around the lens mount - like the old OM1 / OM2 did for shutter speed (if there's space) to make the videographers happy with stepless aperture control where they want it, near the lens, but without everyone needing to splash out on a whole new series of video specific lenses.
Then I'd ask for better integration with tethered displays using whatever new gadgets come along, such as the next generation iPad and the Galaxy S2 HD smartphones. Those gadget manufacturers will improve screen performance and post-processing power much faster than Canon can. Even better if it could be fastened to some hardpoints on the camera, and work with a viewfinder image that wouldn't be out of place in medium or large format. Then there's the opportunity to share the workload of image processing between the in-camera chips and the tethered devices. Maybe do a lot of the post processing right there which usually happens on the PC afterwards. Things like perspective control in software, attaching metadata, geotagging, adding commentary for shot logging, rough cuts or news editing to squirt out over 3G, etc... all of those become a lot easier.
Noted the earlier postings mentioning patents and prior art. None of this is new or especially patentable, it's just putting together pretty obvious things, which already exist, into the mix to open up some new ways of working.