It appears that Marvel are currently in negotiations with Kenneth Branagh to direct the upcoming release of Thor. It would make sense as Thor is known for his Old-English way of speaking and Branagh is known for his adaptations of Shakespearean plays. He would be able to give the script the right feel and also stop the cast from sounding too cheesy.
Like Robert Downey Jr. has managed this year with Iron Man he may also be able to make that leap from B-list actor if he were to star in the film. He obviously doesn’t have the physique to play the mighty hammer-wielding god of thunder but he could play his earthly counterpart, the crippled Dr. Donald Blake. This is all just theory and Branagh hasn’t even been given the role so we will wait and see what develops.