AG said:
5D mk3 = Could become the "video DSLR" taking the best parts of the C300 and 1DX video and putting that into the 5D3 body. Sure it won't be a C300 but it could possibly do 4K but its stills may suffer because of this.
streamline its footprint like they said when they merged the 1D series.
Why would anyone want to buy a camera with 4k video?
Chances are you can't display 4k video on your computer and if you can afford a home-video system with a 4k projector, then money is not a problem for you and you'll buy yourself a camera, today, that can do 4k video.
4k TVs are a long way from being affordable, never mind you actually finding a place to sell you one. The only place I've seen a 4k projector (I was lucky enough to get a demo) was in a HiFi store that has $100,000 amps in the showroom for demo purposes.
By the time 4k video becomes common enough in the home, the 5D3 will be relatively ancient history.
To whit the only people today that would have any serious interest in 4k video are those shooting for the big screen and the big screen only. How many people is that? I'd guesstimate that it would be between 1% and 10% of the total number of cameras sold - maybe not even 1%.
Consider that if you uploaded a 4k video to youtube, nobody that is using a current model laptop will be able to view all 4k of the video and an incredibly small number of people will be able to view it on their computer in full resolution. Well, there's another question of whether or not someone with a monitor big enough will have a computer powerful enough to watch 4k video.
The most likely impact of 4k video, today, will be movie files on your computer that are over 4 times larger than 1080p and that editing the video is consequently that much slower too!
It would seem that 4K video has become a numbers obsession to replace the MP obsession. People need to get over it already.