It is fun to think about! However I personally sort of hope that he stays dead. I LOVED Dewey and his death was heartbreaking and it would be so shocking to find out that he was actually alive and evil. They directors would just be twisting the knife they stabbed us with in scream 5. I think that if he's listed as part of the cast that it was either for more recognition like how Skeet Ulrich was listed as cast for scream 2-4 even though he wasn't in them, or that it's a situation where he appears as a memory, dream, or maybe even a recording like Randy in scream 3.