I actually think the hybrid DSLR / Video will be a huge seller.
1) It will be a very good, full frame stills camera. Probably limited to 12 mp for stills, since that's about the max / ideal mp for good 4K video. For me 12k stills is perfectly fine. I'm sure with Digic V, the still will be top quality.
2) Unlike some people have mentioned, I'm sure you have the option of shooting 2K or 4K video. You don't have to just shoot 4K. Even the current DSLRs give you and SD or HD option.
3) The reason why I like this is because it's more an all around solution. I love Full Frame video (only Canon offers this), yet with this upcoming DSLR, you can still do cool stills oriented stuff like Time Lapse photography (which you can't do with video cameras); and yes, take good photos.
4) It probably won't have the 1Dx 64 pt (is that correct?) auto focus and maybe not as high performing ISO, but will probably be a better stills performer than the upcoming 36mp Since it will have lower MP which translates to less noise. I'd be fine with a 7D style auto focus, even if it does have way less points.
That just means, less cameras to carry around. If you can deal with being limited to 12mp, I think this will be a great balance of both worlds. You'll get top performance in stills and a great video camera.
I agree 100%, that is going to be their moneymaker. Considering the 1Dx is $6800, if you removed some of the still features and added some video features it seems like it would be easy to get it priced around $4k-$6k.