No, probably not. But, in a recent Q&A following a screening of Trick 'r Treat, the Spider-Man actor did reveal that he will be reprising the role of Curt Connors--the one-armed scientist who would one day become the reptilian villain The Lizard--in Spider-Man 4:
Baker said that he had just gotten his first call concerning Spider-Man 4 that very day. Baker appeared in Spider-Man 2 and Spider-Man 3 as Dr. Curt Connors, a professor at Empire State University.
When Dougherty ribbed him about “just appearing in the background” Baker said that, basically, that’s what he’d be doing. It was unclear if they were being truthful or if, in fact, Dr. Connors would become supervillain The Lizard in this fourth entry in the film series. During their riffing, Dougherty used the phrase “cocktease for another year” as to whether or not we’d see The Lizard.
Personally, I can't see The Lizard being a hugely successful villain--at least not on his own. Mainly because I've seen Happiness, and know Dylan Baker the Pederast is a far, far scarier (and tragic) villain. It would be like following up Darth Vader by playing a double-parker.