Niantic has announced that there will be some upcoming changes to Pokémon GO starting during Swinub Community Day on February 16th, 2019 and a major change is Stat Boosts. Full details are in the notes below.

Community Note: Upcoming Changes to Pokémon GO

Trainers, We’re excited to announce a major update to Trainer Battles in Pokémon GO—stat boosts! Starting this Saturday during Swinub Community Day, certain Charge Attacks will have a chance to trigger stat boosts in Trainer Battles. These stat boosts will persist on the affected Pokémon until they either faint or are switched out of battle. The first moves this update will impact are below.

• Ancient Power: Chance to raise the user’s Attack and Defense
• Ominous Wind: Chance to raise the user’s Attack and Defense
• Silver Wind: Chance to raise the user’s Attack and Defense

This is just the first of many updates to come, so stay tuned for more communications about Trainer Battles. As a reminder, Piloswine evolved into Mamoswine during Community Day event hours will learn the move Ancient Power, so don’t miss out!

Source: https://pokemongolive.com/en/post/statbooststrainerbattles2019/