According to James Cameron, the Avatar sequels were such a massive undertaking that he divided the three scripts between the writing team of Rick Jaffa, Amanda Silver, Josh Friedman and Shane Salerno. Cameron delves further explaining the story process: "I think we met for seven months and we white boarded out every scene in every film together, and I didn't assign each writer which film they were going to work on until the last day. I knew if I assigned them their scripts ahead of time, they'd tune out every time we were talking about the other movie."
James Cameron claimed he deliberately set a goal for Avatar: Way of Water and Avatar: Fire and Ash to have a complete two-film story arc, in spite of his plans for a five movie saga, in case no further pictures were made.
Speaking with the French news outlet 20 Minutes (via Culture Crave), James Cameron revealed the third film would introduce a villainous group of Na'vi called the Ash People. "I want to reveal the Na'vi from another angle because [so far] I have only shown their good sides. In the early films, there are very negative human examples and very positive Na'vi examples. In Avatar 3, we'll do the reverse."
James Cameron was prepared to end the Avatar series after this film, if "The Way of Water" wasn't profitable, "The question is: how many people give a sh-t now?" he stated.
According to James Cameron, the Mangkwan are a reflection of the worst elements of the Na'vi. He has indicated that the clan is inspired by the real world, noting that "We [humanity] have a lot of anger and a lot of rage in the world we live in right now. Thematically, the Mangkwan represent disconnection from nature, whereas other Na'vi clans represent connection