I'm over 40. I can't see all the pixels on a 4k display, let alone 8k. I'm still happy with my 2013 MBP w/ Retina.
My plan is to buy a 65" or 75" 8k TV and use it as computer monitor. I'll have a screen that is as big as my desk.
A display of that size will allow me to have my IDE, source control, terminals, log files, the app that I'm developing, my email, the CI dashboard all visible at the same time.
Of course I'll mainly use the bottom center of the huge display, but I think it will be a completely different experience when you no longer have to cmd-tab between apps but can just glance up/left/right to see what's going on.
How far away are you going to sit??
A 75" TV is going to cost you a lot of money for a very ineffective display. It's so large that you'll probably have to physically move several feet to see the edges, meaning that realistically only about half the screen is usable.
I currently have two 27" and three 24" displays on my desk. I already physically move to focus on specific tasks (eg. I have email on a vertical monitor on the side, so when answering emails I'll roll over a bit to the side with my chair).
With a TV, I could have one big seamless area instead.
The one thing that does worry me about the TV is the lack of tilt at the top -- everything in the top half of the monitor will be hard to see because of the angle.
When I work with pen and paper, my entire desk is full of stuff, a dozen sheets and books, printouts and diagrams, all visible at a glance.
I don't see why I should limit myself to a much smaller area when working digitally.
Putting a very fancy lens on a 0.3MP sensor doesn't give you higher resolution photos.
Retinas degrading is a factor of age.