Denmark Disney+ ad has (accidentally?) confirmed the casting of Rosario Dawson and Timothy Olyphant in season 2: https://thedirect.com/article/the-mandalorian-season-2-disney-rosario-dawson-timothy-olyphant-cast
The ad has now been taken down.Almost certain that Ahsoka Tano will be in the show now. As for Timothy Olyphant, of course a lot of people say Cobb Vanth from the Aftermath trilogy; I haven’t read those books in ages though so I’ve forgotten who he is.
Vanth is a guy who acquired Mandalorian armor (presumably Boba Fett’s) and became a prominent lawman on Tatooine.
I hope Ahsoka’s reported role is a glorified cameo or a really meaningful bit part. I trust Favreau’s and Filoni’s judgement and hope they’ll manage to justify the inclusion of all these known characters in the story.