In a recent chat with Shock Till You Drop, Williamson revealed:
"The fourth one is an ensemble. It'll take place right now, 10 years later, and it's going to take place in Woodsboro. We'll have our three main characters [Neve Campbell, Courteney Cox and David Arquette] will indeed be returning for Scream 4.and we'll be introducing several more. We'll also be introducing a little group, a little ensemble of new cast members. That'll take us through the next three."
These tidbits from Williamson have been confirmed via some info that came with the art from The Weinstein Company's American Film Market program. Rumor has it that the new trilogy will be marketed to a younger audience which could mean a PG-13 rating. Though that's usually the first warning sign of an utter fail in horror, Sam Raimi's Drag Me to Hell proved a lot of people wrong. Wes Craven is also rumored to continue the series as director but nothing has actually been confirmed yet.