The teaser further convinced me that I already saw the whole story for the sequel. A really really beautiful and powerful story. People probably get wired why Cameron suddenly do Fast and Furious stuff. But don't forget: Both Terminator 2 and Aliens are family-theme stories. One character may be not related to others, but they act and fight like a family against threats.
Ripley is not the mother of the little girl Newt, but her maternity and the desire for survival led her to fight their way out of the crazy planet. T-800 is not John's father, but he act like an old man instead of killing machine under the influence of the boy's moral restraint. In 3rd act, those characters get together to fight for the people and things they love. For Avatar 2, Cameron is going to do the same. A emotional and powerful story.
Can't wait for this.