Video mode is unimpressive to me at the moment, no matter what body and what manufacturer--it's going to be a while before that technology really matures to the point that I'd get any mileage out of it. Neat to play with, sure, but it's not a selling point yet. On a 1000D, it might be something I'd consider important, but not on a FF body aimed at professional/semi-pro use.
Full weather sealing for less than $3k is the deal breaker. If they can deliver that along side the other EOS standards (menus and whatnot) at some mid-ranged reasonable MP (say 19+) then I'm sold. It would be aces if they deliver an improved internal meter, but I'm not sure how to really define "improved." Less hunting I guess.
It would be nice to have an integrated battery and an intermediate AF system, but I can get by without either (such as the mythical 3D/7D or whatever).
I don't care about the LCD...that is until they're made good enough to truly check color and/or sharpness.
And I want 1/3 stop increments up to 6400.