Yes, she died in the Avatar. But James Cameron's coming up with something. Or so he says.
Look, no one's really going to complain about more Sigourney Weaver, but she died. For some people, that might be a problem. For Cameron, that's just a challenge to be overcome. Said Cameron:
Sigourney and I have a long creative history, dating back to 1985 when we made Aliens. We're good friends who've always worked well together,so it just feels right that she's coming back for the Avatar sequels.
Her character of Grace Augustine, as fans know, died in the first movie, so she's playing a different and in many ways more challenging character in the upcoming films. We're both looking forward to this new creative challenge, the latest chapter in our long and continuing collaboration.
Sister? Relative? Evil twin? She had two bodies in the first film, maybe the not-killed one lived on but is a different person? Or, in all likelihood, she'll play a CGI character that can be easily masked. [Hollywood Reporter]