This is coming from a source that claims to be in connection with Marvel Studios, so because it is really not confirmed, you can just take it as just a rumor for now.
Alan Tudyk may be in consideration by Marvel Studios and Joss Whedon to play Dr. Bruce Banner in The Avengers. The source claims that Tudyk has a pretty good 50-50 chance at getting offered the role, although Mark Ruffalo is the top actor for the role right now, Marvel Studios has been having some doubts about Ruffalo actually taking up the offer and for the time being until they get a definitive "yes" from Ruffalo, they are setting there sights on Alan Tudyk.
Joss Whedon was the one who apparently suggested Tudyk, and since Marvel Studios has been seriously looking into it. Tudyk would likely take up on the offer since Joss and him have worked together in the past.
I wish I could list a source, but I just can't because I have no source to show you guys.
Alan Tudyk could potentially join a cast with the likes of Chris Evans, Robert Downey Jr., Chris Hemsworth, Samuel L. Jackson, Scarlett Johansson, and Jeremy Renner. Another actor that is connected to Joss Whedon is Nathan Fillion, who is rumored to play Dr. Hank Pym in the film, alongside Eva Longoria, who would play his onscreen wife (or girlfriend) Janet Van Dyne. The Avengers will be released on May 4, 2012.