The PS5 will run at 4K thats pretty much without question. But games won't be running in 4K, apart from the less graphically intensive ones. And by that I mean sprite based 2D indie stuff. The normal run of the mill titles I expect to be either 1080/60 or perhaps 1440/30 for the others. You'd then expect the PS5 will upscale to make it look decent on the 4K tvs.
PREDICTIONS FOR END OF 2015: (Made Jan 1st 2015)
PS4 - 34M - XB1 - 21m - WII U -12M