Okay, spoilers ahead if you haven't seen Avatar yet. All six of you.
Avatar ended with the human threat defeated and kicked off the planet and Jake Sully using the massive natural hard drive of Pandora to transfer his consciousness into his Avatar body. This is why James Cameron insists that a sequel to what is now the Biggest Movie of All Time will not be called Avatar 2:
"Certainly I don't want to call it Avatar 2...He's not an avatar anymore, is he? Maybe we'll call it Na'vi."
That title's not going to sell, Jim! You've got to call it Avat2r or 2 Na'vi 2 Pandora or something hip. Don't you know anything about making these blockbuster motion pictures? And then you can cap the trilogy with Avatar: Pandora Drift!
Cameron talked about some ideas for a sequel, but who knows how much of it is real, serious talk or whether Cameron, rightfully high off his enormous success, is just talking out of his butt. He insists that the sequel will delve deeper into Na'Vi culture since audiences have embraced it (some a little too much). He also makes it very, very clear that no one but James Cameron will be touching the sequel to James Cameron's motion picture: