Bruce Campbell has made cameos in each of the Spider-Man movies, but he told AccessHollywood he will play a major role in Spider-Man 4. While Campbell says he has knowledge of what part he will playing, he also told About.com that a movie like Spider-Man 4 is filled with secrets.
That studio stuff, it's all secret. They can't even.... They give you the script, they give you maybe the pages that you have. I can't even learn my own dialogue — that's how secret it is. Like this movie was so secret they wouldn't even give me the script. I'm like, "Well, how am I supposed to act?" They go, "That's your problem."
Director Sam Rami and Sony Pictures have been quiet about what villains will appear in Spider-Man 4, and AccessHollywood speculates that Campbell could be playing a villain, possibly Mysterio. So far, rumors have mentioned Morbius or a combination of Carnage and Electro as the villains, but not Mysterio.
Whatever his role, Campbell revealed that Spider-Man 4 starts shooting in January of 2010. With any luck, he'll know what role it is by then.