Well, despite the disagreements I think there is plenty of logic to 4x the resolution. If I have 30" screens, one current high def and one 4K, the 4k has 4 times as many pixels to display the information. That's how sensors have been marketed and described. Yes, we all know that linear resolution is what really counts, and we all know that it takes 4x the pixels to double that.
But I have no problem with someone stating that a 4K TV has 4x the resolution of HD.
It's all marketing speak, and certainly those marketing are going to color it in the best way possible. Can't blame them ...
One thing I've noticed through the years is people do what they want. If they think they see a difference in a 80mpx back they do, if they think they see a difference in 2k to 4k video . . . they do and they will use the cameras they like, want, can afford, or whatever.
I've shot a truck load of 4k, tons of 2k, usually side by side and went with 4k REDS, not for the sheer resolution, but because of the raw workflow, a 444 file, 12 to 14 stops of dr. The R1's make a great file and give you a lot of room to work and even when edited in 2k I see a difference, but mostly due the professional nature of the file.
In regards to viewing 4k, I don't care. I've seen a lot of 4k projected in every form of media and I don't see enough difference to care.
What I do see with 4k is your storage, processing power from computers, graphic cards goes up in kind. There is no free lunch.
Red's next camera will be 8k and honestly at this point I see that more as a marketing trick rather than anything anyone really needs.
Personally, I view 90% of my entertainment from an Ipad, or computer screen, always download the SD versions for drive space, speed to download and costs. If the production is professional, the editing and coloration expert, I notice that a lot more than I notice 2k, 4k, etc.
I'm not alone in the ipad world of viewing. It's probably not socially acceptable, but I find so many people viewing streaming video on their own devices even in the same room. I can hear my wife in her office listening to one program, I'm downstairs in another office working and watching something else, so if it really is a streaming world I don't think you'll see 4k anytime soon.
In regards to the Blackmagic camera, I wish them well, though know the original black magic had some issues, especially with noise at anything above base iso. The 4k may be better (I hope so) and may be a game changer due to price, though price in motion imagery is all over the place.
Saving 10 grand on a body is a drop in the bucket compared to evfs, monitors on board and off, ssd cards, storage, computers, graphic cards, breakout boxes, mounting rigs, supports . . . well you get the idea. When cinema lenses average about 8 grand a lens, the actual digital brain is not the highest price item in the room.