The Sequel of Avatar :The Blockbuster on 2012

James Cameron and 20th Century Fox talking about filming the Avatar sequels back-to-back

Give Avatar took nearly 4 years to make and cost north of $360 million it would make a lot of sense for James Cameron to do a ‘Pirates of the Caribbean’ and shoot Avatar 2 and 3 back-to-back. It would mean 20th Century Fox can shave a few hundred million off the budget costs and moviegoers won’t have to wait until 2018 for the trilogy to be complete (if a trilogy is their end goal).
In a recent interview to promote the re-release of Avatar later this month Cameron said they are still working out the deals for the next film, and that he is currently taking notes for the script. The director also seems keen on the shooting back-to-back idea.
From MTV:

Regarding his plans and discussions about two proposed sequels, we asked if he’ll shoot them back-to-back. “We’re actually talking about that. That’s not a decision yet,” Cameron revealed. “That is something that makes a lot of sense, given the nature of these productions, because we can bank all the [motion] capture and then go back and do cameras over a period of time.”
He added that the nature of their filmmaking process lends itself more naturally to a back-to-back shooting schedule, versus that of other live-action productions.
“The way these back-to-back productions fall apart is that you’re trying to do two live-action films back to back, and you’re working on it for a year and a half, shooting. Everyone is dead. It’s not humanly possible,” Cameron said of live-action shoots. “This type of film, it absolutely would work.”

One downside to back-to-back filming is that usually the second film is just a filler which leads up to a grand finale in the third film. I’m sure Cameron has big ideas, having previously said he wants to explore the oceans on Pandora next time round, so hopefully both will be worthwhile.