Likelihood is that if this is a "PS4K" and will retail for $399-$499, it'll be the following:
- An incremental upgrade to the current PS4 that is "4K Ready", and able to consume 4K media content, as well as play a very small handful of games in 4K, a bit like how PS3 has a handful of 1080p games.
- In terms of upgrades to current gen gaming, it'll at BEST, be able to play most AAA games going forward at a slightly higher resolution and framerate. For example: Battlefield 5 will run at 1080p/60fps as opposed to 900p/60fps. Assets, textures etc will remain more or less the same across both SKUs. It will be nowhere near a generational leap.
- It will NOT preclude a perpetual state of cross generation. PS5 will be a huge leap over both PS4 and "PS4K".
- There will be no "PS4K" exclusive games. Sony isn't stupid.
If it exists at all, I'd agree with the above assessment about what it's likely to be. The only other difference I could see is integration of the PSVR breakout box functionality to reduce the number of power supplies and tangle of wires required.