alt Hacker NewsI have a 40in 5k (32in 4k, but wider). IMHO, 138ppi is the bare minimum, but it really depends on a person's eyesight and preferences.
I would love a large-ish ultra-wide with > 160ppi. One day, maybe, that being said, by that time those things will exist and be reasonably priced, my eyes might not be able to appreciate the difference.
I'm using three 4k 32" screens arranged vertically, for 6480 x 3840 desktop size.
The only real monitor upgrade I'm willing to entertain is a ~50" 8k curved screen (basically a curved TV-sized screen), which has not been made yet AFAIK. I'm not into "ultrawide", for me it has to be "ultrawide" and "ultratall". I want all that screen real estate in high PPI.
I tried test-driving a 50" 4k TV for a week and the flatness of it was not what I wanted, it has to be a curved screen for workstation use.