News reports say that the new Acer and Asus G-Sync 4k HDR monitors will be released this month... though not UW, they will give us an idea of what HDR brings to the table.
Regarding pricing, a reputable seller in Denmark is listing the Asus PG27UQ at 18995 Krone (£2245) and the Acer X27 at 18495 Krone (£2186). They are taking pre-orders on the Asus, with an estimated stock date of 22 May.
Looking at the current models:
£800 Acer 32" XB321HK G-SYNC V2 IPS 4K Monitor
£600 PREDATOR XB271HU 27" 2560X1440 IPS G-SYNC 165HZ
£600 PREDATOR 4K XB271HK 27" 3840X2160 IPS G-SYNC (60Hz)
I believe 4k at 144Hz is new, which will demand a higher price, but I suspect it is the HDR feature that is pushing the prices up with the new models.
Bringing discussion back to UW monitors, 34 or 35 inch UW monitors tend to cost more than 27" 144Hz monitors and 4k models, so I am expecting the Acer Predator X35 200hz HDR and similar UW monitors to be over £2000.