https://thedirect.com/article/super-mario-galaxy-movie-synopsis-reveals-new-characters

Wario is supposed to be in the Galaxy movie.
They got Yoshi and Bowser Jr (Yoshi wasn't in the trailer but his design got leaked in pic related)

So most likely Wario is the other antagonist in the film. Thinking about it,
>Trailer shows Mario and Luigi on bikes going to the Sand Kingdom
>Maybe they have to get some kind of treasure there, and end up crossing paths with Wario who steals it
Makes sense