Pokemon GO is expected to have a holiday event this year, and players are hotly anticipating the return of Delibird and festive hat Pikachu/others. Info on the upcoming event is not available yet, but we can speculate some things about the event based on previous years.
What Happened Holiday 2018 for Pokemon GO?
Last year, there were four stages to the event, each involving a different bonus:
This boost also included the release of many Pokemon from Generation 4, as well as a boost to Ice-type Pokemon spawns.
What to Expect in 2019: More Unova?
Pokemon that could be arriving this year from the Unova region are likely to be Ice-types. Vanillite, the ice-cream style Pokemon, seems to be a top contender. Last year only a few of the Ice-type Pokemon from Gen 4 were made available, so Pokemon arriving in this upcoming wave may not be associated with the winter season.