The tricky thing about adapting Stephen King's IT novel into a movie, is that it's a pretty expansive book, split into two distinct volumes. The first volume of IT takes place when the protagonists, The Losers Club, were just kids; however, the second volume of the book takes place when those same characters have aged nearly thirty years, and are very much adults.
For the IT movie franchise, this presents a unique challenge. Films become popular because of the the actors and characters involved, but a the IT sequel will essentially be giving audiences a new movie, with adult actors playing the characters.
King's novel does feature the adult version of The Losers Club returning to Derry to try and reconnect with childhood memories, which leaves the film version room for flashbacks. So, are the child actors of IT making a return for the sequel? Director Andy Muschietti answered that question in a recent interview with Variety:
"We are going back to the summer of 1989 and if people love these characters and actors the way I do, it’s going to be a blast to go back to 1989 in the second one," Muschietti said. "I don’t want to go back just for that, I want to make those flashbacks essential in the plot where in order for the Losers to figure out the clues to defeat Pennywise, they have to retrieve their memories from the past."
If that final part sounds confusing, it's probably because you don't know that a big part of IT's story deals with The Losers Club losing their memories of Pennywise as they grow into adult - a fact that's teased in the film when the adults of Derry have trouble seeing Pennywise like the children can. In any event, it will give the talented young cast of IT plenty of reason to come back and entertain us again.
IT is now in theaters; the sequel will soon be going into development.