Niantic just announced that Pokémon GO is set to got more Pokémon.
Niantic and The Pokémon International will reveal details next week for more Pokémon coming to Pokémon GO. Details for this will be available on December 12. This will be the first addition to the game for more Pokémon.
Pokémon GO is available on iOS and Android devices.
Source: God is Geek