that is all assuming that you only use 27 inch...While the move to 4k cant happen soon enough. I think 8k is overkill. For your average desktop monitor size that is. Obviously if it's really wide that's another story, 2 side by side 4k screens is fine.
Really it comes down to how good is the human eye. And the number of pixels you need depends on distance to the screen.
Average human eye visual acuity is about 1 arc minute(20/20 vison). The people with the best eyes can go down to about 0.4 arc minutes, but you would have to have like 1 in a billion vision to get down that low.
At 2.5 feet, which is a common desktop viewing distance. An average person can resolve about 115 ppi. And someone with the very best vision on the planet can see about 300.
A 1080p 16:9 27" screen has about ~82 ppi. So thats not enough to meed the 2.5 requirement for the average person at 2.5 inch.
A 4k 2160p 16:9 27" screen would double that to 164ppi. So that covers the average 20/20 person at 2.5 foot. Its 40% better then you need at that distance. But it doesnt cover the truely exceptional eyesight case. Id say this covers 99%+ of the population of the earth tho.
The people with truely exceptional vision could make use of a 8k desktop screen. But almost no one would be able to tell the difference between a 4k and 8k desktop monitor at normal viewing distances.
Now lets get back to the real world. In the real world, the best of the best graphics cards can barely do 4k. So, who cares about 8k at this point.
And to get back to even more reality.....8k is bigger then 4k so it must be better...im sure all the ifans will love it and scoop it up.
Edited for language by moderators