Check https://pokemongo.com/en/gofest/tokyo
Seems the other two go fests in Chicago and Copenhagen doesn’t have more info available yet, but Tokyo seems amazing.
Some highlights from a quick glance:
All unown letters in the wild
Shiny wash rotom
Mewtwo and shadow raids with backgrounds
Shiny Paldean tauros
Tokyo backgrounds will be available
Special 2026 merch featuring mewtwo
by powergirl11