I mean if you want your Geralt to be black in your head cannon (despite the fact the books say he's pale due to mutations): Be my guest, I couldn't really care. But the fact is, the books were based in the "north." The books didn't have an "eastern" country like Ofiri (IIRC) that was introduced in Hearts of Stone/DLC 1 for the Witcher 3 which introduced 2 middle Eastern-looking characters. Who's to say that the Witcher 4 wouldn't have Ciri dashing further south than Nilfgaard to a new country like Ofiri?
I mean shit, CDPR retconned
spoiler (click to show/hide)
Regis'
book death to have him pal around with Geralt in Blood and Wine, there's nothing stopping them from doing that and going "their country is further south than the Nordic/Nilfgaard conflcit seen Witcher 1-3."