I shoot Panasonic and Nikon, and so have no dog in this fight, but I suspect that the only place you might see a faint difference between a Nikon D800 and the Canon would be in yard-long prints. So, let me give you some basic "pro" thinking about this problem. "Do I make yard-long prints? No." Now, there may be a few people who actually sell yard-long prints, probably numbering in the dozens, but for the rest, the megapixel count will mean almost nothing. For one thing, most people can't print well enough to make much of the difference in megapixel count. I haven't handled the camera, but the sample pictures I've seen suggest that it'll be a good, solid, high-ISO camera that might be better thought of as a cheaper, and perhaps slightly better, competitor to the new Nikon D4.
I have to say, though, that I really don't see the point in the emphasis on film-making. If I were a film maker, I'd get a movie camera. If I were a pro photographer who wanted to expand into video, I'd get a movie camera. If I wanted to take video pictures of my kids, I'd get a (cheap) movie camera.