one last thing: companies like Apple look "where the ball is going." Regardless of what the display market is like today, the ones sold next year, and the year after that, will be incrementally better. Eventually 4k will become obsolete and whatever replaces it will be better. That's where Apple is going aim.
Apple have been aiming at 5k since 2014 and the ball still hasn't got there yet - at least not in terms of gaining traction in the PC market. A bunch of third-party 5k displays from HP, Dell, Phillips launched back then but sank without trace, apart from the LG one which was promoted by Apple to Mac users.
27", 4k UHD at typical viewing distance puts the pixel size at the limit of 20:20 vision - and that applies to pixel-sized artefacts from fractional scaling, too. Many people
will see more detail/sharpness on a 5k@27" screen, but you're in to diminishing returns -
especially on Windows which (for better or worse) has freely adjustable UI scaling and so doesn't share the Mac's 220ppi "sweet spot" - 5k on PC is a bit nicer than 4k but probably not worth 2-3x the price. I think the other problem with 5k on PC was that it initially needed either two DisplayPort 1.2 cables or Thunderbolt 3 (and a compatible GPU). We'll see if the new, more affordable, Asus 5k makes inroads, now DP 1.4 and/or TB3 are more prevalent on PCs - I don't get the feeling that the Samsung has been flying off the shelves, though and I somehow doubt that the PC world will embrace 4k - I suspect these displays are still going to be mainly targeted at Mac users and will have to fight against the "look and feel" of the Studio Display.
Thing is - as with a lot of IT - technology is starting to catch up with demand and the mk1 eyeball, the days of struggling with flickery, 30Hz, 320x200 screens are long gone and 4k is now very close to "good enough" for most purposes. 5k is already a busted flush - and what talk there
is is about 8k or HDR/HFR. I don't even see 8k breaking out as a mainstream tech for computer displays and traditional domestic TVs (4k TV is barely worth it below about 50") unless someone comes out with affordable, wall-sized screens or projection systems.
Instead - "the ball" has been going towards other refinements than simple resolution, like high dynamic range, improved colour gamuts, higher frame rates via OLED/QLED/microLED etc. These are starting to show up in 4k panels and smaller laptop or tablet screens, but I fear that Apple's attachment to 220ppi
on the desktop is a bit of a stumbling block there - expensive "niche" panel sizes for tech like miniLED and OLED
and huge bandwidth requirements (5k is already considerably more bandwidth than 4k, now double the frame rate...).
You can hardly call the Studio Display forward looking... It's, well, slightly brighter but otherwise the same tech as the 2017 iMac/LG Ultrafine and only an incremental improvement in gamut/surface treatment over the 2014 iMac. Pro XDR is already 5 years old.