Looks like it, based on previous footage. This is going to be a GIANT roster for a 2D Mario platformer (Mario, Luigi, Yellow Toad, Peach, Daisy, and four colored Yoshis as opposed to the typical Mario Bros., Toad(s) and/or Peach).
I'm not overreacting, you're overreacting!
I guarantee you that if Rosalina isn't in this even as a cameo, she's going to be important in the inevitable sequel. (Although they didn't announce a voice actor for Rosalina with the rest of the cast and yet they mentioned who the voice actor for...
There is no possible combination of words to adequately describe how excited I am for this. I've literally been waiting for this my whole life and I even did a drawing of the penguins an hour after seeing the teaser.
I don't care what you say, who you are, or what you think, you cannot spoil or...
I heard a rumor that they're doing away with the New Super Mario Bros. series and replacing it with something new.
Also it's supposedly going to be a very GameCube oriented direct.
Don't really have many expectations, but I can always hope for a Miitopia sequel.