1080Ti will be okay for 4K. It's currently the fastest gpu out there, so there isn't much choice right now. Just know that you will have to lower a couple settings if you want to keep a constant 60fps. However, I believe that 4K works best then you have a large >40" screen. If you're planning on sticking with the standard monitor sizes, then I believe 144Hz 1440p will be a better choice. What you lose in resolution will be gained in motion clarity, framerates, and responsiveness.
On the processor side of things, an overclocked 7600K is one of the best gaming processors, so if you come across a game that runs on one or two cores, and both of those cores are at 100%, then there's nothing you can really do about it unless you lower some settings. 5% IPC bumps from generation to generation won't be enough to fix those situations.
For me, Volta will be the architecture I'll stick with for more than one generation. Pascal is just a placeholder when it comes to 4K. 4K 120Hz+ will be out next year, and while big Volta won't be able to produce numbers twice that of a 1080Ti, it will allow for greatly improved minimum framerates in demanding games. Fast sync will introduce less stuttering due to the extra frame sample size, and input lag due to low framerates will be better due to the framerates being higher overall. If Volta is blessed with HDMI 2.1 and TV companies release OLED 120Hz 4K TVs next year (you'll need HDMI 2.1 for that type of panel), then that will be the ideal combo imo. That's what I'm waiting on.