I think it's a excellent post-modern homage to Western Culture. Our mortal voices will live on forever through the glowing interconnected tree of digital media, or something, provided we can keep the capitalist militia from fucking it over in blind pursuit of profit. And maybe, if we clap hard enough, we can upload our heroes in such a way that they can live on forever with us in mutual respect and freedom.
The sad thing is, of course, that this celebratory path around Western Culture is so thoroughly trodden that it only looks new if you throw 3D laser-cut CGI sets and costumes at it. Like a crowd-pleasing opera. This is not Cameron's fault; stories this fundamental need telling and retelling every generation.
Avatar is about as good a vehicle for the "culture will set you free" story as any action movie will ever be, and I think we'll look back on it as Cameron's masterwork. He's no Hitchcock, but he knows how to reach his audience. That he finally gets them to root for the aliens/indians/hippie-tree-huggers instead of the cowboys makes it worth every penny.