Sigourney Weaver has spoken to getthebigpicture.net about the possibility of sequels to both Avatar and Ghostbusters.
On Ghostbusters 3 she spewed, "I have yet to read the script. I've had a couple of calls and I know they're rewriting and all I said was that I hope my son, Oscar, has grown up to be a Ghostbuster and Ivan Reitman said yes. Beyond that, I have no idea. I hope it comes together, but we already did two wonderful films and, if we have to let this one go, that's fine." But what of Avatar? She bought the farm in the first film and few people saw her character coming back. But not so according to the woman who was Ripley: "Don't worry, I will be back. Jim [Cameron] says no one ever dies in science fiction. He's told me the stories for the next two movies and I have to say that they're absolutely wonderful and there's a real treat in store. Now we just have to make them."
Personally I'm a lot more excited by the possibility of a Ghostbusters 3 than Weaver returning for Avatar 2. She'll probably appear like some sort of floating Obi Wan Kenobi, offering advice. Avatar 2 must be a few years away regardless - nothing has been mentioned about a start date.