During the Pokemon Direct today, Game Freak announced that Pokemon Sword and Shield will be getting expansion passes. Each game will be getting it’s own pass, so if you own both you’ll have to buy it twice. During the direct they showed off two expansions, The Isle of Armor coming June 2020, and The Crown Tundra coming Fall 2020. Each new expansion promises new story, characters, wild areas, legendaries, and old Pokemon returning.
The expansion pass is $30, and that includes both The Isle of Armor and The Crown Tundra. Again if you own both games then you will have to buy the pass twice.