I made the transition to 4k from 1440p several years ago when I got into Digital Photography, I got a true 4k 4096-2160 so it had a little bit more width to the screen, a proper 4k format. I don't play too many FPS games, so a lot of city builders, MMO's, dungeon crawlers and top down strategy. I had a 1080Ti I upgraded from a regular 1080, and running games at 60fps was pretty hard even with the Ti. It was miles away from the other cards, but you still couldnt get 60fps on several titles with max settings. When I upgraded to a 2080 Ti, it was a big jump in FPS and would play most everything at 60fps. I have a few games I still can't get 60fps on, but even then, It doesn't matter as its not an FPS.
I have an OC'd 2080 Ti and an OC'd 9900k. Even then 4k gaming is still rough if you want at minimum 60fps on EVERYTHING. Was spending $1500 on a 2080 Ti worth it? To me? Yeah. I also do photography and spend most my time on my computer, so this is like anyone elses hobby that they end up spending a good chunk of change on.
If I wasnt willing to spend so much, I could definitely say the 2080 Ti and all the other things you'd want to buy isn't worth it if you really arent even sure you care about 4k.
I love it though. Since my monitor messed up, I've been using a 55' LG C8 OLED TV with HDR. God damn gorgeous picture. You should see SC in HDR / 4k 60fps. Its quite nice. Little did I know the newer 2019 LG OLED's come with g-sync and 4k 120hz. Missed out on that goodness by a year.
So yeah, you're looking at spending a lot if you're someone who want's to push the fidelity to the max. Is it necessary? I'm sure 1440p would be "fine", but fuck that. I can't ever go back. Im actually pretty mad right now just because I think Nvidias new cards, especially their top end card is rumored to beat the 2080Ti by half, and up to 70% in some titles performance wise. If that is true, that is insane. And also intel's new processors are using another socket type, which means I'd have to get a new motherboard if I decided to upgrade the CPU to another Intel. This probably means I'll build AMD next time unless intel can convince me otherwise. Watching those threadrippers dominate media benchmarks does tempt me.