I'll note that Sony is using PS3 -kiosk models for driving digital signage in the commercial domain .. possibly quite unsuccessfully, looking at the pricing we received.
I have, well the company I work for has, just quoted a simple 120" Digital signage wall (2x 2x 60" Bezzleless Panels) which is in total 2560x1440p, and many commercial panel models 46-55" are coming in 2x2 x1080p = 4K2K
I don't doubt that 4K2K will be heavily used ... whether it's by consumers is a totally different kettle of fish
Anyone using a 2x2 PC screen configuration will definitely use 4K2K ... if that is over a single HDMI v1.4 or single display port, with the monitors automatically arranging, that would be nice .. but wishing too much.
Probably won't happen, but we can dream
At any rate, if anyone under 30 sees a 4K2K screen, they might suggest that 1080p is a little too low def in comparison.
If you build it, they will come. 1080p is nice, but it's not impossible to see the difference on a semi large screen.
I'm mid-30's and I can tell the difference between 720p & 1080p on my tiny 46" TV.
The local theatre, I noted, is projecting at 720p on a very large screen. Another 4K2K application.
At any rate, if the PS4 is capable of rendering 4K2K at any decent frame-rate, it can easily render 2k1K with ease. Future-proofing perhaps ....