King, who portrayed twins Goldie and Wendy in the first film, also said that she expects to return for the sequel in some form.
"I hear so many things, between the cast and Robert [Rodriguez] and Frank [Miller], because Frank's like my brother," King revealed, according to Comic Book Movie. "They hired a new writer, an Oscar-winning writer, to work on the draft."
King was referring to the hiring of The Departed screenwriter William Monahan, who was brought in earlier this month to make final revisions to Miller's script.
"That's what I've been told, yes," King said, when asked specifically whether she will be part of the film. "I don't know for sure now, because they're having a new writer come on."
At Comic-Con International in July, director Robert Rodriguez suggested that the film could begin shooting before the end of the year.
Rosario Dawson recently claimed that the sequel would honour Sin City star Brittany Murphy, who died in December 2010.
Watch one of Jaime King's scenes with Mickey Rourke from Sin City below: