Apple set the bar with the iMac 5K. We have to wait for the display manufacturers to catch up to it; as well as a new display port standard to actually use these. So my advice is to wait it out.
The display manufacturers (or at least one of them, I’m guessing Sharp?) are the ones that supplied Apple with the 5K display for the iMac. I wonder if there was some kind of exclusivity deal / contract signed for some period of time?