To the above poster frustrated with HD video in stills camera. I can see where you are coming from.
But for Canon, video is being so stressed on the 5D3 is because one of the main reasons why the 5D2 sold so many copies is because it was the first camera with HD video that your could change lenses, get a nice shallow DOF and actually afford to buy.
Here in LA, I work in Television and know numerous people who have bought the 5D and 7D only because of the video. The stills aspect was just a bonus.
The race is on now between Sony, Canon and Panasonic to make excellent Still / video hybrids because it's basically the future. Nikon is the only hold-out on the video thing, and I feel people are starting to by-passing Nikon because of the video issue.
Canon sees this new market they accidentally created and they need jump on it because they are already falling behind Panasonic. Canon was really surprised by how many people embraced the 5d2 video.
Plus, I'm sure the video presents a new, interesting challenge for Canon engineers. Still cameras are already really good, but for affordable pro HD video, it's still really just getting started.
I just hope the 5D3 video is a big step up from the 5d2, or else Canon will lose the market for sure.
I'm sure the stills and video can co-exist and both sides will win.