From imdb.com:

Dan Aykroyd has confirmed the third Ghostbusters movie is all set to go before the cameras – with the original cast in place to reprise the characters from the 1984 film.

The movie star reveals Sigourney Weaver has signed on for the project, alongside himself, Bill Murray, Harold Ramis and Ernie Hudson – and the film could start shooting this winter.

Aykroyd still fears the project could “blow up” “at any second” but he hopes the new film will herald in a new generation of all-girl Ghostbusters.

He tells the Los Angeles Times newspaper, “I’d like it to be a passing-of-the-torch movie. Let’s revisit the old characters briefly and happily and have them there as family but let’s pass it on to a new generation.”

And the actor wants Alyssa Milano and Eliza Dushku to consider becoming part of the Ghostbusters family: “I think they’re amazing.”

I’ve said it before and I’ll say it again… I’ll believe it when I see the first production still. Until then, as Akroyd put it, the movie has a big chance to “blow up” and never happen. With so many stars involved, including the rumored return-to-acting from Rick Moranis, it seems like all the talk of Ghostbusters 3 is simply fueled by the hype of the franchise reaching its 25th anniversary next month. If the project survives the hype surrounding the anniversary, highly-anticipated upcoming video game (for which the above-referended Alyssa Milano lends her voice), and long-awaited release of action figures featuring the actors’ likenesses, then I’ll start to believe it’s actually going to happen.