Currently, 4K gaming with only one card is not really stable unless you are satisfied with an average of 30-40 fps.
I advise you to either use SLI or wait a little longer. I myself have a 1080Ti and for this reason I decided against 4K and got a 2K monitor where I have over 100 fps constantly. In comparison, with 4K, the average is quickly down to 60 fps.

Kind regards
Izzy

I usually manage 50-60 fps in 4k High settings