The Mandalorian season 3, episode 7 footage was shown at Sat Wars Celebration, and the footage description teases Grand Admiral Thrawn's debut. Originally created in the Expanded Universe, the powerful Star Wars villain was brought back to canon through Star Wars: Rebels. The show's ending has left mysteries about what happened to Thrawn since, and The Mandalorian season 2 used Ahsoka to tease that he is part of the larger plans that Jon Favreau and Dave Filoni have for the Mandoverse on Disney+.
https://screenrant.com/the-mandalorian-season-3-episode-7-footage-description-spoilers/