Thanks to Mew’s appearance in Pokémon Go, more pocket monsters from the Kanto region – aka, the first-generation Pokémon – will appear in the game over the next week.
From today until April 17, Pokémon from the Red, Blue, and Yellow games will appear more frequently for players to catch. Trainers can earn double the candy from any action involving those regional creatures. Additionally, Aerodactyl, Snorlax, and other stronger Pokémon from the region will be available to catch in raid battles.
Hopefully after this event we will get the shiny Pokémon recently discovered through datamining.
[Source: Pokémon website]