Well the 980 ti is pointed towards 4k gaming, however personally I don't think it will max all games at 4k.
Here are some benchmarks:
http://www.tested.com/tech/pcs/529725-testing-geforce-gtx-980-ti-4k-benchmarks/
The 980ti from those benches delivered very playable framerates
here is some more: http://www.maximumpc.com/nvidia-geforce-gtx-980-ti-review/
So from these I would say yes, you can game quite well at 4k, however at maxed settings your experience (depending on the game) is not the best, as it does drop below ~35fps. However drop a few settings down, possibly to medium and you'll get over 60fps in most games
I've seen a friend play BF4 on his 980ti at maxed (no AA, it's not needed at 4k) and it handles it easily at over 60fps.
Quick answer: yes but not maxed for all games, however very satisfying.
If you were to SLI I would bet on MAX on every game out now. Although on some benches even with SLI the min fPS was still low.
-good luck
the 980ti is no slouch at 4k.