4k gaming is clearly a pipe dream atm, the amount of time it would take to model things is unthinkable... however it will be the next step after PS4 I'm sure, maybe by then a few million people on this earth may own these displays...
What I'm hoping will be possible on the PS4 for is obviously Full 1080p 120hz in 2D for all games. I'm not even sure if any televisions currently actually accept true 120hz feed, there's actually only a handful of monitors that can... from what I've read the foreseeable future in PC gaming will be aiming at that, so PS4's GPU better be able to handle that at least... very important for high speed games such Gran Turismo... it should then be able to run at 85fps with zero st u t ter.