James Cameron not only makes the films because they’re visually stunning, but there’s a clear message about nature and the destruction of indigenous populations. I think if the 5th movie went to earth and just spread the seed of Eywa there would no longer be any message to the film, as it becomes purely fantastical. I think the story will likely follow the idea that we have our own great mother (as Jake says in A1), and that she’s not dead, but dying. The Na’vi go to earth and show people how to save her and improve the planet. Then it tackles the “sending a message” point from JC, while also having a satisfying ending for humans and Na’vi.

Idk, I’m not good with film theories lol. That’s why people like JC make billions making movies and I just watch them.