Generation 5 Pokémon are officially available to be caught in Pokémon GO, meaning that Niantic will be gradually releasing all 156 Pokémon from the Unova Region, first introduced in the Pokémon Black and White handheld games. With these new Pokémon will come brand new regional Pokémon that will only be available in certain parts of the world, making the task of filling your Pokédex more challenging than it needs to be.
Firstly, the three elemental monkey Pokémon will all be region-specific. Pansage, the Grass-type, will only be available in Asia. Pansear, the Fire-type monkey, will only be available in Europe, the Middle East, Africa, and India. Finally, Panpour, the Water-type monkey, can be found in the Americas and the country of Greenland. This also means that all three evolved forms, Simipour, Simisear, and Simisage, will be region specific, making them the first regional Pokémon with evolutions. Whether or not you'll need a Unova stone to evolve these Pokémon, or if you'll just be able to use candies, is yet to be announced.
On top of the three monkey Pokémon, Heatmore and Durant will also be region-specific. Heatmore, the Fire-type anteater Pokémon, will only be available in the Western Hemisphere. On the opposite end of the world in the Eastern Hemisphere, Durant, the bug-steel ant Pokémon, will be available.
These five Unova-region Pokémon will be added to the current list of regional Pokémon, making the task of completing your entire Pokédex even more difficult with each generation. Luckily though, Niantic often holds special events where you can obtain regional Pokémon outside of their given region, just like the event going on currently, where you can obtain a Mr. Mime, Tauros, Kangaskhan, or Farfetch'd without having to travel to their respective regions.
As of now, only a limited amount of generation 5 Pokémon are available, as Niantic tends to gradually release certain Pokémon instead of putting the entire generation into the game right off the bat. Today, you can catch Snivy, Tepig, Oshawott, Patrat, Lillipup, Purrloin, Pidove, and Blitzle. Although Pokémon GO is quickly catching up to the mainline games, and will eventually run out of new generations to introduce, it's great to see them constantly working to keep Pokémon GO fresh, which is a big reason that has contributed to the game's continued success.