Since I'm a video guy, I want the 5D3 to have
1) no terrible moire and aliasing like it currently does
2) 60p slow motion
3) Better video codec, preferably 50mb 4:2:2 at the least. There are rumors of RAW codec to an external recorder, but RAW is not a major concern of mine. For work we work with RED regularly, and we rarely color grade from RAW. Usually just color grade from the proxies in After Effects, which ultimately link up the source file. So for me at least, not too worried about RAW as much as a good in-camera codec.
I just hope the 5D3 or a decent video camera comes out at NAB. Canon is making me really nervous lately with how quiet they are. Sony and Panasonic are releasing and announcing all this new and progressive stuff, and it's been quite a while (last 7D) since Canon has released any cameras of merit.
Since Canon hasn't announced any press releases for NAB yet, it's looking like they won't release anything at NAB for the 2nd year in a row. That is so embarrassing and really makes us video guys lose hope in Canon who is started to get dusted by the competition.