I can finally write some shit about it since the update is out :> And FYI, this is based on the White/White2 version of Opelucid City, since the Black/Black2 version has a drastically different aesthetic.
BW-shared verse headcanon: I imagine the city being spilt down the middle, and is half White!Opelucid (The older, more history based/focused city) and half Black!Opelucid (urbanised and technologically advanced.
Of course, it’d be a gradual shift in the city, not like suddenly, older city, then new city.
Alternatively, it could be done like cities in real life; mostly modernised but with lots of older building dotted amongst the centre then getting older around the outskirts of the city. Either way, it’s some sort of merge that just seems to work, idk