>>36036836>seeing stuff like Ultra Ruin, Ultra Desert, and Ultra Forest in HDYes please.
I'd be hard pressed to imagine an in universe justification to visit Ultra Space though, like in ORAS they had portals that are implied to be from Hoopa, in USM they had Ultra Space and alternate dimensions as an excuse to bring back all the Legendaries. I feel like they've now pigeonholed themselves because now they gotta do that and also find a way to bring back the Ultra Beasts. Like
>>36035647 pointed out it might just be easier to shoehorn them all into one place, kind of like how a lot of the Legendaries in USM shared a spot depending on their type (like most of the flying Legendaries being in the cliff world).
Alternate option: Retcon the UBs so that Ditto can breed with them, or have UBs be able to breed with each other (but only the same ones, so two Guzzlords together can make another Guzzlord). This ensures that they don't actually HAVE to keep putting in Ultra Space in future games and you can just breed the ones you already have or ones that you got in a trade. The reason I bring this up is because if they're regular, common Pokemon in other dimensions, it should stand to reason that they have to exist and multiply somehow. Restricting them to either Ditto or the same species as themselves would at least prevent them from learning fancy Egg Moves.