The fantasy blockbuster sequel's future was thrown into doubt due to Stewart's fling with married director Sanders earlier this year. David Koepp has apparently been working on a screenplay for the follow-up that would bring back Stewart's Snow White and Chris Hemsworth's Huntsman.
According to RadarOnline, Universal plans to put the sequel before cameras in 2013.
"The script has already been written and production will begin late next year," a source is quoted as saying. "However, Rupert Sanders definitely won't be a part of the project.
"Rupert didn't want to be a part of it to begin with because he is desperately still trying to save his marriage. The search is still on for a new director."
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The insider added: "Kristen is extremely concerned about her acting career. Other than the Snow White sequel she isn't attached to any other projects. There are scripts coming in, but not as many good ones as she would like. It's distressing to Kristen that Rob is attached to four separate movies over the next year and a half."
Snow White and the Huntsman grossed more than $390 million at the worldwide box office this summer.
Photo gallery - Snow White and the Huntsman in pictures: