Back in mid-September, Sigourney Weaver was asked about the possible return of her character, Grace, in Avatar 2 to which she replied, "Don't worry, I will be back. [James 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."
No surprise there, like she says, it's science fiction and anything can happen. However, it doesn't seem Cameron will be getting too crazy with Grace's return as he spills a few more details in a new interview with Vulture after receiving the Breakthrough Award from "Popular Mechanics" on Monday night.
When asked about Weaver's character returning Avatar 2 and 3 Cameron asked, "[Have] you ever heard of nonlinear storytelling?"
He goes on to explain, "A lot happens on that planet before she shows up, and before Jake [Sam Worthington] shows up to join her. She's there for fifteen years ahead of time. I don't know, but I wouldn't jump to conclusions. And I've already said way too much about Avatar 2 and 3 here and there, but people piece it together like those voice cameos and tell the whole story!"
So it sounds like we're either going to be looking at prequel material or flashbacks or both. Personally I wouldn't be surprised if Avatar 2 was a prequel of some sort that suggested an alternative for the Na'vi after their home tree was destroyed as well as introduces a long-ago enemy of theirs and then Avatar 3 explores that alternative and has that long-ago enemy return now that the humans are out of the way. Just spit-balling.
Cameron said in the press release announcing the two follow-up films that each would be "self contained stories that also fulfill a greater story arc," but as far as any story specifics are concerned an exploration of Pandora's oceans in the second film is really all we've heard of.
Cameron was quoted back in April 2010 saying, "We created a broad canvas for the environment of film. That's not just on Pandora, but throughout the Alpha Centauri AB system. And we expand out across that system and incorporate more into the story – not necessarily in the second film, but more toward a third film."