Need advice on my 3rd monitor and 4k resolution :)

So, I'm currently in situation where I need to buy another monitor for my PS4 Pro and future consoles.

I have budget of around 520-550$, and I'm thinking of either buying normal monitor with 122hz , or 4k monitor 30"+ with 60hz

I didn't want to end up selling normal monitor after 1-2 years because of next-gen consoles, and wanted to utilize full graphic abilities of PS4 Pro. I simply wanted to future-proof my monitor, but buying 4k monitor with this specs seems like waste too.

Any advice ? what would you guys do in my place ?