O.k, maybe I should elaborate a little. In the first Sin City, Clive Owen played Dwight in a segment called The Big Fat Kill. This story is actually the third book in the Sin City comic series, and is preceded by A Dame To Kill For, which sees a much different Dwight, in look and personality, caught up in shady dealings that end with him getting facial reconstruction surgery. So this makes the sequel (or part of it, since the movie tells four separate stories) a prequel.
Following on the heels of the announcement that Joseph Gordon-Levitt has joined the cast as Johnny, Josh Brolin will be stepping into the shoes of the new (or is that old?) Dwight. I wouldn't be surprised if Clive Owen made a brief appearance, just to clue tin those audience members who find themselves a bit lost.
Sin City: A Dame To Kill For will be released October 4th 2013 (U.S.)/ ? (U.K./IRL)
via Dimension Films