I mean what is the point of double or quadrupling the pixels only to show content the exact same size as on a lower resolution display?
I mean I just bought a laptop with something like 3200 x 1400 resolution, but then Windows UI is scaled at 200% so all the content is the same relative size as if it was a 1600 x 700 display. This is the same process used by iOS devices that went "Retina", same sized icons, just smoother rounded corners.
It has been maybe 15 years since I last looked at a screen and lamented how aliased some lines looked on it.
Yes I know that there is content like video and photos that will look beautiful @ 5000+ pixels, and I am sure there are apps that can use every pixel you can throw at it, but 99% of the time most users are going to simply be looking at a highly scaled up UI that is identical in physical dimensions to icons and buttons from the previous "low" res generation of screens, they just paid an *ssload more money for that privilege.
Also, I question putting this on an iMac because iMac's are not notorious for offering high-end GPU options and if you hope to play any future game on this screen, at native resolution, then you are going to need like a 4-way SLI GPU configuration option from Apple.com. Unless you can add an external GPU through Thunderbolt which also daisy chains back to the internal iMac display, then I think most people are going to be frustrated trying to make full use of their iMac with an impressive waste of pixel count.
Apple, just focus on making iMac affordable and/or come out with a headless Mac that doesn't cost as much as a used car and let people decide how many pixels they need to waste on a display of their choice.