Honestly, I feel like buying into a 6-core CPU right now is something that will likely age poorly, particularly if you're taking a 5+ year look. The major consoles now have 8-core CPUs and developers are going to start taking advantage of that. Also going from an 8C/8T CPU to a 6C/12T CPU is probably a side-grade unless you get a Zen 3 CPU.
Anandtech has the 11600K in their bench already and it's frankly a
wash in gaming compared to a 9700K. There are also some benchmarks where the older 9700K still beats out the 11600K as well, so it's hard to recommend.
If the OP were primarily gaming in 1080p, then Zen 3, even a 5600X, would offer and uplift in several titles. However, at 4K everything will be GPU bound. Also, LGA 1200 is pretty much dead at this point, so buying a new Intel CPU now means you'll need to replace the board if you want to upgrade again soon. AM4 is also probably at the end of its life as well so buying in now for what's mostly a side-grade seems similarly bad.