It also introduces a new character which will wreak havoc on the humans in the film... The character will pretend to be a lowly helper but instead just by being himself things do not go well for the humans on the planet.http://thecelebritycafe.com/feature/%E2%80%98avatar%E2%80%99-sequel-already-planned-01-14-2010
James Cameron has had a sequel for Avatar planned from the beginning.
Karla Casillas
“Avatar” director James Cameron told Entertainment Weekly that he has a sequel planned for his box office hit. It’s something he’s had in mind from the beginning, he said.
“I’ve had a storyline in mind from the start—there are even scenes in ‘Avatar’ that I kept in because they lead to the sequel,” Cameron said. “It just makes sense to think of it as a two or three film arc, in terms of the business plan.”