This is an opinion with a mix of speculation
A lot has been made of the “in development” announcement of a new “Cinema” branded DSLR. Most people seem to think the camera is going to be based on the 1D X.
I agree with Keith at Northlight Images, nothing was said by Canon as to what the form factor would be. I think what they showed was just a 1D X body with a red “C” stuck on it for marketing purposes.
I think the camera they're speaking of will sit between the 5D Mark III and 1D X. Perhaps an EOS 3C? I do not like the name “3D” for a camera that doesn't actually shoot 3D.
I also don't think it would be a full size EOS-1 body. They just spent a few hours touting the small stature of the C300, I don't think they'd make a cinema DSLR bigger than it needs to be. I'd have to hear from cinematographers & videographers whether or not a camera the size of the 5D Mark II is preferred to the EOS-1 body.
What about photographers?
I know a good majority of photographers are pretty tired about hearing about video in DSLRs. A lot of the community is looking for a new “photography first” full frame DSLR that doesn't require remortgaging their homes. I think the 5D Mark III will be that camera. It'll probably have video features on par with the 1D X, but will be a high resolution, high image quality still photography camera.
I've said before that I think Canon plans to monetize the videographers and video DSLRs, so something like the “EOS 3C” makes a lot of sense. Looking at the prices of the new cinema lenses, it seems videographers have no problem spending more.
So don't be worried photographers, Canon hasn't forgotten about you and I'm sure will deliver the product we all know you want.
It's going to be a very interesting 2012 to say the least.
This was just an opinion post, please don't be too hard on me.