Quoted By:
>what if there were only 151 Pokemon?
But the franchise still continues after gen 1. The series just turns more Dragon Quest-y, where the region, story, and gameplay update with every sequel, but the monsters stay largely the same. New forms are still added for the original 151 when they need them for plot, like I dunno a Dark Squirtle attacks a village and now Dark Squirtle is just a Pokemon that pops up in every sequel without needing any justification. Mewtwo and the legendary birds get expanded lore and become more plot relevant in sequels.
Then some of the sequels start going in weird-ass directions, like having one be computer-themed with a society of Porygon living on the internet and you capture digital copies of Pokemon.