In an interview on the MTV Website Frank Miller appeared to confirm that Sin City 3 would be based on Sin City Book 7: Hell and Back, a notion that co-director Robert Rodriguez had previously advanced.  All this talk of a third Sin City film came while production of the second film in the series was on hiatus until after Miller finishes his Spirit movie and Rodriguez completes his remake of Barbarella (see 'Sin City 2 Delayed'). 

Miller remains confident (as he should considering how financially successful the original Sin City film was) that Sin City 2 will get made and he told MTV that he full expects to make Sin City 3 as well.  While the second Sin City movie will be based on A Dame to Kill For, the second book in the series, Sin City 3 will adapt the most recent Sin City saga, To Hell and Back, which centers on Wallace, a brooding artist given to hallucinations, who, thanks to his military training, is skilled in his use of violence.  While Miller wouldn't comment on possible casting for Sin City 3, a smile crossed his face when a reporter asked him about the persistent rumors that Johnny Depp would portray Wallace.