I guess it makes sense to talk about "High DPI", because there is a kind of barrier. "Resolutions" or more precisely pixel counts kept getting higher and higher

I guess it makes sense to talk about "High DPI", because there is a kind of barrier. "Resolutions" or more precisely pixel counts kept getting higher and higher for years, until they stagnated at 1920x1080. Display vendors couldn't go higher, because consumers would complain that "everything is too small". The reason is that the majority of software plays like it's still 1995 and you have 640x480 pixels. Everything is a fixed pixel size, not a fixed physical size. I'd say that all displays with a resolution (here I mean dpi) so high that its uncomfortable to use with current desktop programs are "High-DPI". Once the software is changed to allow arbitrary dpi scaling, there will be no barrier, so there is no low or high dpi anymore, just higher dpi. (And ultimatively, as soon as you can't see individual dots anymore, it won't make sense to increase the dpi further.)