Ah, the joys of shooting stories out of sequence!
Mickey Rourke is in negotiations to return as Marv in Sin City: A Dame to Kill For. It's essentially a done deal, according to all involved, and it will see the character--who was executed in the electric chair at the end of Frank Miller's Sin City--to return to the screen. That's good, becuase he was fans' favorite character and it would be difficult to do a sequel, a decade on, without returning to some of the most beloved faces in the original film.
Both Miller and co-director Robert Rodriguez (also known as "the movie guy" in the director's chair) will return to take on the second film, which is largely based on the graphic novel of the same name, but will also incorporate elements of new stories written for the screen by Miller. In A Dame to Kill For, Clive Owen's Dwight and Rourke's Marv are central characters who storm the estate of the abusive husband of Clive's lover. Owen is reportedly likely to come back, although there's no indication he's signed on yet, or is even in formal negotiations.
Sin City: A Dame to Kill For will be in theaters October 4, 2013.