From what I've heard it won't do games at 4k, but it will be able to play 4k movies. Not sure in what format(s) or any other details though.
You wouldn't really want it to do games natively at 4k anyway. The (large) amount of extra GPU cycles it'd take to render at that resolution would mean it would have to draw a lot less stuff. So the world/characters would be simpler.
PS: Been lurking this board a bit at random lately and have been meaning to say hi. So...hi everyone! :-)