Sigourney Weaver spoke to Channel 4 News ahead of Avatar's premiere. Weaver, who appeared as Dana Barrett in the first two movies, said that she is unlikely to have a big role in the third movie but did say that her character's son Oscar and Peter Venckman will play key parts in the sequel, but she did reveal a possible huge spoiler regarding Murray's character.
"I'm afraid to say it [Ghostbusters 3] is happening, I hope people are excited about that. I don't know if I'm going to be in it, I have had a couple of calls asking 'would you read the script'.
"I know that my little son Oscar – who was kidnapped from me – I think he has grown up to be a Ghostbuster.
"I might be in it; I see nothing wrong with being in it, although I don't think I will have a big part. I think Bill Murray has a little more to do with it - he's a ghost."