Greendale is back. Really there isn't a lot to say. Chevy Chase supposedly left the group at the end of last season but we know that's not going to last.
Chang is now a member of the study group and quite possibly a member of the security team.
It looks like the class for the year is going to be Biology since Biology 101 is the name of the first episode. We all know that John Goodman is joining the show this year as the Vice Dean of the tech school. Presumably Troy will be exploring more of his natural talent for the trades.
Other than that I have no clue whats going to happen this season.