Saw an article on that new Globus Mondi (?) shop--can't remember if here or a Potter site--that said Universal does not have the rights to Fantastic Beasts. I assume the same goes for Cursed Child. Until we hear differently, assume anything being built is from the 8 movies.
Which makes thematic sense in any case. Potter London is a perfect snapshot of the city mid-90s (having lived there half a year in 1993). A book store, a record store, the old red phone booth--it's as much a time capsule as Main St. USA. I have no problem with everything in the WWoHP being frozen in a particular era.