The Pokémon Sword & Shield Expansion Pass will be released as DLC for $29.99 USD. It will be divided into two parts, but you will receive both parts for your respective game. The Isle of Armor is scheduled for June 2020, while The Crown Tundra, which is scheduled to be available in Fall 2020.
Isle of Armor
Story has you training as an apprentice at a dojo under master Mustard. Features new rivals, Klara (Poison-Type user) in Sword and Avery (Psychic-type user) in Shield.
New legendary: Kubfu (Fighting-type), evolves into one of two forms of Urshifu: Single-Strike Style (Fighting/Dark-type) or Rapid-Strike Style (Fighting/Water-type)
Adds Gigantamax versions of Rillaboom, Cinderace, Intelleon, Venusaur and Blastoise.
New character items customization items are also included!
The Crown Tundra
New legendary: Calyrex (Psychic/Grass type)
New Co-Op mode allows you to explore Pokémon dens with Legendaries from past games returning
Other new legendaries are included as well, some of which include what appear to be Galarian forms of Articuno, Zapdos, and Moltres (the bird trio from Kanto), and additional members of Hoenn's Regi trio (though it's unknown whether these are Galarian forms or entirely new Pokémon).