Pokémon Storage has officially been increased in Pokémon GO. Niantic is now allowing players of its immensely-popular mobile game to hold a maximum of 5,000 Pokémon. To gain more storage in Pokémon GO, you can purchase more Storage Upgrades via the in-game shop. In addition, you can now expand your item storage to 4,000 in Pokémon GO.
Source: @PokemonGoApp
Source: Pokemon