When you get as rich and as famous as director James Cameron, you can pretty much do whatever the hell you want for the rest of your life. (Maybe not serial murder. But I bet you could get away with just one.) That's why, for example, Cameron was able to take time away from the movie business to take a self-financed solo jaunt to the deepest part of the ocean. This also means Cameron has the freedom to stick to passion projects for at least a little while; this is the time in a famous director's life when he can do all the weird stuff that was kicking around in his brain for years while he directed action movies about killer robots/aliens/chunks of ice.
(Think Francis Ford Coppola and Youth Without Youth. I never said these weird things would be good.)
And now that Cameron has this incredible freedom, he's decided to spend the rest of his directing career… making Avatar sequels. Like, a lot of Avatar sequels. Please don't ask him to do anything else, all he cares about is Avatar. Avatar Avatar Avatar:
Last year I basically completely disbanded my production company’s development arm. So I’m not interested in developing anything. I’m in the “Avatar” business. Period. That’s it. I’m making “Avatar 2,” “Avatar 3,” maybe “Avatar 4,” and I’m not going to produce other people’s movies for them. I’m not interested in taking scripts. And that all sounds I suppose a little bit restricted, but the point is I think within the “Avatar” landscape I can say everything I need to say that I think needs to be said, in terms of the state of the world and what I think we need to be doing about it.
Cameron's actually exaggerating a bit, here: for one thing, he's attached to direct the film adaptation of the manga series Battle Angel Alita. For another, he's still going to make documentary features. (My guess is that they will be about the deep ocean. I know I'm going out on a limb there, but I like to take risks with my prognosticating.) But rest assured that Cameron will still have freedom when it comes to narrative filmmaking, because every story can be told using ten-foot-tall blue-skinned cat aliens and hackneyed noble-savage archetypes. That's Screenwriting 101, pretty much.