So far Mario, Luigi, Wario , Waluigi and DK are confirmed playable.
Petey is confirmed to be a boss.
Peach, Daisy and Rosalina are safe and so are Yoshi and Bowser so they might reveal them next.
the characters that aren't safe are : Toad, Toadette, Dry Bowser, Bowser Jr and Sprixie.
I would assume they will cut Dry Bowser and the Sprixie in favor of other characters.
The sprixie is surely a goner because she is more like a ''wii u'' character since she belongs in 3D World ... Dry Bowser is a cheap clone so its 50/50 for him.
But like i said, since animations from US are returning there's little excuses for cutting characters like Bowser Jr for example