I gathered this from Movieweb all credit to them.
Avatar 2 and Avatar 3 will film together as a single large production released a year a part
"It's in progress right now. There is a lot of writing, there is a lot of a designing and a lot of tech work that we are going to do. What I can tell you is that our plan right now is to make Avatar 2 and Avatar 3 together as a single large production released a year a part. In order to do that, we have to refine our technical process beyond the end of where we were when we were finishing Avatar, so we are taking our time now. Partially because going through the process, even though we refined that process as we went along, there were certain things that we would have had to go full stop to be able to improve and upgrade and we are in that process now.
This is what he said about the resurrection of Sigourney Weaver
"Who said she died? Nobody dies in a science-fiction movie. Whether Grace lives or dies depends probably more on Sigourney's agent than anything."
So what do you think of this should they bring Grace back?