According to the British tabloids, "Christian Bale, soon to be seen as the caped crusader in The Dark Knight, is in talks about donning the jolly Lincoln Green outfit of Robin Hood, where he will be part of a menage a trois between Russell Crowe's Sheriff of Nottingham and Sienna Miller's Maid Marian.

Nothing is signed for Bale, but director Ridley Scott is exceedingly keen to cast him.
Costume fittings begin next week, so he'll be either in or out by then. Vanessa Redgrave and William Hurt are also in discussions about being in the film, which is called Nottingham."

This of course, is a rumor from a tabloid, so take it with a grain of salt, however, this does sound interesting. I really enjoyed the way Bale and Crowe worked together on 3:10 to Yuma and think that this movie would probably be a decent success if it happened.