Scream 3 had the WORST reveal of the killer in all three of the films, and it was no surprise that the franchise ended there. But now years later they are picking it up again in hopes of re-invigorating the film series and in a recent podcast in chatting with Matthew Lillard (killer of the first Scream movie) it was revealed that he was originally intended to return as the killer of the third film as well.
Now of course spilling this plotline that was scrapped from part 3 also means it wasn’t used for the premise for Scream 4, currently in production. Had Lillard been invited back as a surprise killer for 4, I doubt he would be talking about it online.
I still think it makes logical sense that they should have made Sidney the killer, bringing her story full cycle, but the more images they release of her getting chased down and attacked by Ghostface, it is seeming less likely to happen.
I would have preferred the ending to Scream 3 that Lillard describes.