Avatar: What will human-beings' motivations be in Avatar sequels?

The first 'Avatar' movie dealt with many themes, and introduced several different concepts to the audience, as well as plunging us into a vivid technicolour universe. However, the whole premise of the first 'Avatar' movie revolves around one single premise, the desire of the human 'invaders' to acquire the valuable 'unobtanium' mineral from rather inconvenient locations with the Pandora habitat to which the Na'vi are native.

via Yahoo Movies UK – Movie News | Film Reviews | Movie Trailers http://uk.movies.yahoo.com/avatar-human-beings-motivations-avatar-sequels-231000997.html