Are you talking about stills or video? If stills, and you mean something more than 7680×4320 pixel size, then you don't actually need to go crazy with hardware. It depends on what you are likely to want to do, and where you think you might take your image editing in the future.
I have a 50Mb Canon 5DS and a six year old 3930K six core system with 32Gb of memory, and basic image editing barely makes it break into a sweat. But a multi layered project of more than 5000 pixels on the long side, can slow it down. I have had projects that pretty much became too slow to continue, and which I shelved for when I get a faster computer, so you can see how it depends on what you want to do.
I am not sure I'd want to edit 8K video with Photoshop though. If I'd spent megabucks on a RED Epic, or whatever model that shoots 8K video, I'd be using Premiere Pro and some serious hardware. It's all a matter of balance. I also wonder if the current GPU shortage is real enough to affect the sale of high end desk top systems?
As Trevor says. 8K translates to standard resolution for high-end DSLRs today. Nothing special.
Thank you for the link. It was of great help.
And thanks Trevor for the detailed info.
I am looking for Still photo retouching and each of my file will have sizes upto 2 GB.
I also have a large number of layers and in most cases will be doing the retouching in 300-400 % zoom.