I use a 980ti @4K and have no problems. Most of the games i play are maxed out (with lowered AA) pushing 40-60FPS. Examples include: Assetto Corsa, Just Cause 3, Dirt Rally, GTA 5 and Fallout 4, although I run slightly lowered details for some things on Fallout.
It's surprising how much easier to run games become when you turn down AA since you don't need it as much at 4K.