Blizzard has only released one real expansion for Hearthstone since the game’s release, which was the Goblins vs Gnomes expansion. While adventure updates do include new cards, there is only a small amount added to the game and so they do expand what is available card-wise in Hearthstone, it isn’t like a full expansion such as Goblins vs Gnomes which added 150+ cards. It appears that Blizzard may be teasing yet another expansion for Hearthstone, this time themed with pirates and ninjas.