High School Musical 3's role in movie trivia history...

Has any other widely released theatrical sequel ever had its previous edition(s) NOT also released in theaters?

Surf II :wink:

Hamlet II?

Not quite what you’re looking for, but the closest I can think of are same-cast reunion movies of TV shows (as opposed to big budget remakes with different casts) that were released theatrically. X Files and Sex in the City are the most current ones; STAR TREK was possibly the first of the really big budget ones. (The Munsters and other shows had same-cast big screen versions as well, but they were usually low budget.*)

There were several movies that first aired on TV during the anthology days, but were remade for screen: No Time for Sergeants and The Miracle Worker [originally a 1 hour teleplay] and Marty are three that come to mind.
Was Eddie and the Cruisers ever released theatrically? I know it didn’t really gain a following until home video (often credited as the first movie to become a hit on video). I believe it’s sequel was released theatrically.

Yes