Actually, some games run just fine at 4K in Windows -- e.g., Alien: Isolation is entirely playable at 3840x2160, for instance, although it's smoother at 3200x1800 and looks just as good. Depends on the game, although you're more likely to find yourself winding up at 2560x1440 for a lot of newer games. Regardless, it'll look just fine, since the display has enough pixels that the scaling's not obvious.