I'd say upgrading would be pretty high on your list, atm the 980ti is just fine (hell I can run games on decent settings with my 960, OCd) but even if you don't bother with 4k gaming the games would still catch up. Obviously you'll be fine for a while but I'd recommend upgrading just to avoid future hassle, and then not have to upgrade again for a long while.
EDIT: probably upgrade once the inevitable 1080ti comes out