This article contains spoilers for Avatar: The Way of Water.Avatar: The Way of Water explains why the Na'vi will likely come to Earth in Avatar 5. James Cameron's Avatar films are set on the lavishly-created fictional world of Pandora. There, humans are repeating the same mistakes they have made on Earth; they are attempting to plunder Pandora's natural resources, ranging from the rare mineral unobtainium to the precious glands of the whale-like tulkun. But now the conflict is becoming an existential one for the native Na'vi, because humanity is aiming to claim Pandora as a new homeworld.
The Earth briefly seen in the first Avatar film was a poisoned dystopia. "They killed their Mother, and they're gonna do the same thing here," Jake Sully warned in one memorable speech. According to Avatar: The Way of Water, Jake's assessment of Earth is now shared even by the rich and powerful, and they have decided they must leave Earth and move to Pandora. Humans have returned to the moon, establishing a new city from which they can expand. The end of Avatar: The Way of Water saw Jake commit at last to resisting them, and he will inevitably lead the Na'vi in a war. There have been constant rumors it is one that will see the Na'vi visit Earth itself in Avatar 5.
The Na'vi Will Visit Earth As Redeemers, Not Conquerors
It's difficult to imagine a scenario where the Na'vi visit Earth, simply because they have no interest in pursuing that kind of technology or military ethos. Jake's continued faith in human science is portrayed as a weakness rather than a strength in Avatar: The Way of Water; he summons doctors when his adopted daughter Kiri is left in a coma after a mystical experience, and his faith in science blinds him to the significance of this event. In thematic terms, then, there's no way the Na'vi will ever embrace interstellar flight and head to Earth to wage war there.
But Kiri is the key to the Avatar saga. Cameron deliberately surrounds this character with Messianic imagery, complete with a miraculous conception; her mystical experience (or, as human science would put it, her epileptic seizure) is analogous to a baptism. She appears to have been born of Eywa to serve as a bridge between the Na'vi and the Sky People, because her body is uniquely adaptable. She is able to survive underwater for extensive periods of time, and her body even seems more suited to human environments than the Na'vi norm. She is also the only one of the Sullys who considers Spider part of the family. Kiri is uniquely positioned for a Messianic "ministry of reconciliation," one that will surely mean she winds up going to Earth.
The Avatar Films Could Be The Story Of Earth's Salvation, Not Its Defeat
This explains why the Avatar films will inevitably head to Earth. The humans and Na'vi are becoming locked in a cycle of violence, and it will be up to the next generation - including Kiri - to free them from it. This means the resolution of the Avatar saga lies not in conflict, but in redemption; not in hostility, but in peace. Kiri will presumably become something of an ambassador figure, perhaps somehow restoring Earth with the help of Eywa. This would fit with Cameron's environmental themes, but also with the sense of optimism and hope that runs through the franchise as well. It would mean Avatar 5 will be a film redolent with hope, in which Earth is saved and not defeated; and that potential is set up perfectly in Avatar: The Way of Water.
