Reitman, 67, directed actors Bill Murray, Dan Aykroyd and Harold Ramis in both Ghostbusters and Ghostbusters II, but the director announced in March he'd only be participating as a producer in the latest installment of the saga following Ramis' untimely death in February.
"The studio is in, and we have writers working on it as we speak," Reitman said when asked about the upcoming flick. "We're hoping to film at the beginning of next year. Dan Aykroyd and I meet about once a month to talk about it."
Asked whether Murray would reprise his role in the film, Retiman explained that while he's "publicly said no," the actor, with whom he's worked on six films, "never says yes until literally just before the shoot."
"Two TIFFs ago, we had a late dinner at Sotto Sotto, and we ate and talked until 4:30 in the morning," Retiman recounted. "I told him, 'I don't care if you do Ghostbusters—I mean, I'd love it if you did—but why aren't you doing leading parts for big studio films?' He said he didn't want that responsibility. He wanted to be a character actor.
Aykryd, the film's creator, announced in July that production on Ghostbusters III would begin in 2015.
"It looks like we'll be in pre-production in the spring now, from what I'm hearing," he told Carson Daly at the time.
The first Ghostbuster film was released in 1984. The sequel, Ghostbusters II, followed in 1989.