https://www.polygon.com/2017/10/16/16482748/pokemon-go-gen-3-new-pokemon-halloween-event-2017

Pokémon Go’s big Halloween update could bring some exciting changes to the game, based on findings from big-time dataminers in The Silph Road guild. These range from bug fixes to anti-cheating tools, but the grabbiest one is our first look at what could the game’s first third-gen Pokémon.

A splash screen found in the game’s latest file package shows several ghost- and dark-type Pokémon, like the familiar Gengar, Zubat and Murkrow. Also included in the new assets are several Pokémon from the third-generation games: Dusclops, Duskull, Sableye, Shuppet and Bannette.