James Cameron has confirmed that he's going to begin filming Avatar 2 now that he's completed writing Avatar 5. That's not a typo. He's written Avatar 2, 3, 4, and 5 and will be filming them all simultaneously. He told The Daily Beast:
"The thing is, my focus isn't on Avatar 2. My focus is on Avatar 2, 3, 4, and 5 equally. That's exactly how I'm approaching it. They've all been developed equally. I've just finished the script to Avatar 5. I'm now starting the process of active prep. I'll be working with the actors in the capture volume in August, so I'm booked in production every day between now and then."
This is incredibly optimistic thinking on James Cameron's part. Avatar came out eight years ago so it's not exactly riding a wave of popularity. And to follow it up with not one, but four sequels right off the bat is basically insane. What do they do with the three extra sequels if Avatar 2 bombs? Just call it a billion dollar loss and move on with their lives? Does James Cameron go back to the Titanic wreckage and then just stay there permanently?