My idea for Avatar 2

it is a few years after avatar 1.
jake is struggling with his new role as leader of the People.
a new rival faction of anti avatar extremists is rising, on the other side of the planet and gathering a huge army to attack jake's encampment due to the belief he is a fake and illegitimate navi who led them into a war that killed thousands. tensions rise quickly and could explode into war at any further provocation.

meanwhile an alien ship crashes near hometree's wreckage.
these new aliens are humanlike in nature, scientists on a mission. jake learns they are the ratka, and they come from the planet pandora orbits.
the crew is mostly intact and they set up defences, surrounded by the native extremists. they desperately fight to survive. they calculate they'll all be dead soon unless they can reach the other half of the broken ship and send out a distress signal to the rest of the fleet.

jake arrives there and negotiates with the stranded crew, but inform them not all the clans are favorable. he has a plan however to adopt them into an alliance for the sake of peace. the ratka are however debating amongst themselves whether to attempt to call for reinforcements or peacefully integrate.
meanwhile deep in space, the massive human armada gathers to avenge the massacre at pandora and destroy anyone else they find there. pandora is about to become the epicentre for the greatest epic battle the galaxy has ever seen.
jake is forced to make difficult decisions and risk everything in order to save everything he has come to love, from destruction.