In the sequel, Bumper and Fat Amy will hook up.There was some hinted chemistry in the movie that never really went anywhere that could be made up for in the sequel.
Also in the sequel, the Bellas and Treblemakers will have to team up for some reason.Perhaps for a competition or deciding to end their rivalry.
Bumper is not really gonna be a back-up dancer for John Mayer.It was something set up by Benji so that he could get rid of him and join the Trebles.
Beca and Chloe will at least kiss in the sequelThe writers will at least acknowledge the Fan-Preferred Couple even if they don't end up together
The part of John, the commentator, was written for Fred Willard, but they couldn't get himReally, compare this performance with Willard in Best in Show, and you'll see what I mean.