BCB, the 1080Ti will struggle with 4k. My 1080Ti is sort of struggling with 2k 144hz 27" screen.
I like my settings on high and even though I blame the game, I am getting 60-70 FPS in ROE.
I have played dying light and was getting 120FPS.
If you think that you may get a 2080Ti in the future, then the 4k one is the best bet right now.
Do you really need 144hz as your old TV definitely wasn't 144hz.
Remember that once you go black you never want to go back.
Same thing applies to 144hz. Once you have a 144hz screen, if you go back to playing 60hz in games, you loose your sh*t within an hour and rage quit.
Don't ask me how I know cause I am not gonna tell you.