>>34124904>>34124938They could stick around since they were created as an excuse to create Pokemon that look different from normal ones.
>Mr. Ohmori: With the Ultra Beasts, Ken Sugimori, who oversees the Pokémon designs, came up with the concept of doing things we typically avoid when creating new Pokémon. For example, taking the soft texture of a jellyfish and pairing it with glass, or taking something that normally looks small and weak—like a mosquito—and making it super muscular. With these kind of concepts, we were able to create Ultra Beasts that give a very different impression to the Pokémon that have been created thus far.
Plus they need a reason for wormholes to appear in the next generation and it'd be stupid to keep creating monsters for that reason alone.