It's probably a matter of demand vs cost; I'm confident technology can make displays at a higher DPI, but... why? If it's not for consumer use (e.g. 4K, now 8K screens which are IMO completely gratuitous), if they can't scale up to produce millions of panels, it's not worth the investment beyond the research of whether it's possible.
Anyway, the next frontier is (has been?) VR, which needs / needed high DPI but small screens.
The only area where I’d think we want more pixels would be in medical imaging but even then we can always zoom out the interesting parts of the image (and rely on machines to look for interesting parts)
Anyway, the next frontier is (has been?) VR, which needs / needed high DPI but small screens.