And now for the philosophical take.
http://www.billmuehlenberg.com/2010/01/07/the-worldview-of-avatar/
The above link is a take on the Avatar worldview. How come all Hollywood future films portray a pretty dim view of the world as it 'evolves'. They acknowldege the hoplessness and sinfulness of man in thier product without even knowing why.
Well it might be a good that Hollywood is recognising "the hopelessness an sinfulness of man", but I don't reckon you can eke 6 movies, a bazillion books and spinoff series as well as a line of toys and household items out of this 1 movie. And I'm guessing they wrapped things up fairly well, so there's not much chance for a lot of development. I think the closest they're going to get to a saga is this prequel novel that Cameron's writing.