Up until 2013 i was running 1600p or 2560x1600, thats when i got hooked on 4K with the 32" ASUS PQ321. Now after “used up” the ASUS and three ACER 32" G-sync 4K monitor i decided to jump the bandwagon and go big but not ultrabig, ACER CG7 43" 4K 144hz pushed by a EVGA 2080Ti FTW3. Don´t regret it one second and only way i will change monitor is that a 50"+ ultrawide 4K 144hz monitor ever hit the market. I dont need the ultrahigh FPS others like to have, so with that background i say 4K is the way forward if you have the GPU power or the money for it.
Currently having 3 32" 60hz 4K monitor and one 43" 4K 144hz monitor in service as i once did tripple 4K with 32" 4K monitor.
Kind of scared to loose FPS by replacing a 7900X@4.6 with the upcoming Ryzen 5900X from AMD, at least until they get the simulator/game in to shape.