A few months ago, it wasn't clear whether Robert Rodriguez's 'Sin City: A Dame to Kill For' was ever going to happen. Now, not only does the movie have an October release date, but it has considerably beefed up its cast in the last few weeks. Joseph Gordon-Levitt came aboard earlier this month as the gambler Johnny, followed shortly by Josh Brolin taking over the role of Dwight from Clive Owen, d…