While he naturally wouldn't reveal who the villain is in Spider-Man 4, director Sam Raimi told MTV what their thinking is behind the villain they will choose:
"What we're trying to do right now is really understand the journey Peter is going to go on this time and have the villain maybe be a counter to that growth, something that he has to overcome," Raimi said. "Or maybe he has to grow in a way to overcome the villain, because there always seem to be stories of coming of age, of a young man growing up and learning things about life, so once we are identifying the exact movement that Peter has to grow to, I think the villain—and we're trying this right now; we're trying to choose a villain based on who would be the proper counter to that growth, so we really have dramatic conflict."
You can check out the full interview here. Spider-Man 4 is scheduled to hit theaters on May 5, 2011.
Source: Superhero Hype! and MTV's Splash Page