We've known for a while that James Cameron is working on two Avatar sequels however Deadline reports that this has now been upped to three. They report that three high-level screenwriters have been employed to get the movies shot simultaneously, which if pulled off will be really impressive. Production will reportedly start next year, with the release of the first sequel coming in December 2016, and the next two a year after each other. The sequels will be produced by Cameron and Jon Landau.
On the movies Cameron said
Building upon the world we created with Avatar has been a rare and incredibly rewarding experience. In writing the new films, I’ve come to realise that Avatar’s world, story and characters have become even richer than I anticipated, and it became apparent that two films would not be enough to capture everything I wanted to put on screen. And to help me continue to expand this universe, I’m pleased to bring aboard Amanda, Rick, Shane and Josh — all writers I’ve long admired – to join me in completing the films screenplays.”