Zuuyi said:
And 4k capture is only 11.5 Megapixels; which is done by all current Canon DSLRs excluding the 1D3. So 4k capture isn't that big of a deal for a camera.
Simply having a bazillion pixels on the image sensor is not the same as being able to pull image off those pixels for 24, 30, or even 60 frames per second. Have another look at DSLR shooting rates if you don't think this is the case - none of even the top-end cameras come close to 24 frames per second, and the shutter / mirror mechanism is not the only limiting factor here - the electronics are. The data throughput potential of the system, to be exact.
This is part of the reason why the news about the 1D X not skipping lines on the sensor is such big news - getting information from every portion of the sensor rather than just skipping lines to save data throughput (from the image sensor to the CPU, mainly) and processing time (as the CPU combines adjacent pixels from the image sensor into one pixel - remembering that this is done across lines, so this might be a call out to slightly slower off-CPU RAM, as opposed to a simple addition or multiplication on the CPU combining two data points that are "next to each other" in the data stream) is very expensive computationally.
4K stills - yeah, that's not a big deal (anymore - it wasn't too long ago that even stills didn't reach that resolution, and buying a camera with 4K resolution is still not dirt cheap). 4K video is a whole 'nother ballgame.