With Alan Taylor taking over Patty Jenkins as the new director of Thor 2 there now needs to be a rewrite of the current script, and Marvel supposedly already has the man - Robert Rodat.
Rodat, the screenwriter for Saving Private Ryan, is being reported to rework a draft already submitted by Don Payne. It is also being reported that Disney is going to start work on the film later this year for it's 2013 release.
