After multiple viewings of The Avengers leaked trailer and the release of multiple promo posters by Marvel today at San Deigo Comic Con. I am thinking that we are getting a tip off by Marvel as to part of the plot of the movie. The trailer shows everyone who is a part of the team. Marvel also released 6 posters that showed: Iron Man, Captain America, Thor, Hawkeye, Black Widow, Nick Fury with Agent Colson and Maria Hill. The interesting thing is who is missing from both of these forms of media. Who you are asking?? Well the answer is: THE HULK.
We know The Hulk is in the movie in some capacity and my theory is he will be manipulated by Loki to cause havoc and destruction. I think the team will be brought together to first stop the threat of the rampaging monster but he will not be the main villain as I think Loki will be the evil force to drive the film, just as he was back in the Avengers comics in the beginning.
I am going to post the link to the 6 posters below.