How is it remotely possible for pokemon to run out of ideas? There's literally billions of unused animals. Even if Pokemon were to strictly only release 1 pokemon per genus even when it comes to evolutionary lines they still wouldn't be able to run out of animals for centuries to come.
That's ignoring that there's already multiple pokemon based on the same animal, and pokemon not based on animals at all.
This is IGNORING massive animal groupings such as beetle, theropod, fish ect that would mesh together to the uninformed player