From Anandtech:
http://www.anandtech.com/show/10663/analyzing-sonys-playstation-4-pro-announcement
On that note, while Sony is pitching the console for 4K video and gaming, Mark Cerny was rather clear that to reach 4K gaming, they expect developers to make significant use of both spatial and temporal anti-aliasing/reprojection.to reach 4K. In other words, most of the time the console won’t actually be rendering games at 4K. This makes a lot of sense; all else held equal, the PS4 Pro needs to fill 4x as many pixels with a GPU that’s (at best) 2.3x as powerful.
This means that the number of games that natively render at 4K is by necessity going to be relatively few. Games could still render at resolutions over 1080p (e.g. 2560x1440), giving them more fidelity than current 1080p games, but various upscaling/reprojection methods will have to close the gap to 4K. Given that even the best PC GPUs have only recently reached the performance level to render the necessary 8.3Mpixels without significant quality compromises, and we’re likely a generation (or more) from consoles being able to reach that same level.
My gaming PC I use 2560x1440 now - my TV set renders down that down to 1080p very well. I can't tell the difference from resolutions above that so there's no reason for the card to work harder. It is interesting to see how my card performs at the higher resolutions, though.
If I was to get a 4K TV (using it as a desktop monitor I would be able to tell the difference), the games are still more or less developed for 1080p, plus my RX 470 doing games at 4K with anything turned on, the fps starts to plummit.
Not complaining since I got it for $175. But retailing for $200, it is possible to make a $400 console out of this. From what I'm hearing the PS4 Pro is built upon an RX 470 GPU.