Holy shit! Buried in an interview with THE TROLLS directors Walt Dohrn and Mike Mitchell (which also revealed the writer of SHREK 5), there is a quick mention of a possible SKY HIGH sequel. Here's the interview (relevant info at :42):
I for one am super pumped about this possibility. While this is obviously not a confirmation, the fact that there's even talk of a sequel is exciting. I f*cking LOVE SKY HIGH. It can be difficult at first to get past the Disney-channel level production values and special-effects, but once you do it's a really enjoyable ride. It's not only a fun superhero story that was obviously made by fans of comics (with some great lines, like "Some get powers by being bitten by radioactive insects…or they die"), but also a sweet coming-of-age story. The characters have multiple dimensions (and like BREAKFAST CLUB, and other great teen movies, we eventually look past their cliques and see the true person underneath), and the film merges superheroic action (with some suprisingly cool fights) with teen melodrama better than anything I've seen.
Not to mention the really fun performances from the adults. There's Kurt Russell (as a dopey Superman stand-in), Bruce Campbell (as a mean gym teacher), and KIDS IN THE HALL alumni Dave Foley (who is the "sidekick teacher" Mr. Boy) and Kevin McDonald (who gives a great performance as the strict science teacher who used to be a villainous mad scientist, another nice detail).
I mean, it is a kid's movie (there's no one drinking alcohol during a party scene, the main villain's plan involves turning people into babies, and there is a poop joke), but it doesn't deter from the film's fun characters or cool setting (it's called Sky High because it's a floating school that moves around so villains can't find it).
Anyway, I urge fans of both teen movies and superheroes to look past the production values and some kid-centric humor to see a great underrated gem. Hopefully then I won't be the only looking forward to this sequel.