It's happening! Polygon says that the Johto Pokemon are slowly but surely making their way to Pokemon Go! The event starts with players finding eggs at Pokestops. When you find an egg, be sure to hatch it as soon as possible as it could contain either Togepi or Pichu! Niantic also adds that trainers should be able to find a "festive Pikachu" around their favorite romps. This Pikachu with a Santa hat will only be available for a limited time, but the developers say most trainers should have no trouble finding and capturing one before the promotion ends December 29th. 

No word yet as to when the full roster will debut...but I would expect well see them before Christmas.