It is definetly a horrible time to buy a monitor. If you buy one you'll be stuck on lower rez or lower refresh or smaller size, and not just by a little, by heaps and bounds.
We've been stuck on 27 inchers or without any decent HBR3 capabilities for a really long time, as monitors seem to evolve a lot slower then other hardware.
Pesonally I have been on 27", 2k wide for better part of the decade already and would really like to make the jump to something like 30-35", 4k, 120-144 Hz and can't. There is literally nothing for me to upgrade to.
Better to wait well until next year, maybe by the time the new monitors come out the rtx 3xxx series and the rx 6xxx series cards along with the CPUs and some decent mobo revisions, if not models, will be available.
The monitor manufacturers have completely dropped the ball on 4k hardware, even moreso then GPU manufacturers with their availability woes.