Another possibility that occurs to me is that she is Eywa incarnate; that the transfer actually worked but in the wrong direction causing Eywa and Grace to switch places, making Eywa a sapient person and not just a cross-species super-organism.
Not a super-organism exactly. She was already established to be a global thought transfer network that seems to exhibit an unspecified form of super-intelligence, with character-assumed sapience. Super-organism wouldn't make it that different from Earth, and I don't think it technically qualify for one, either. Nitpick aside, I think if there are tests for sapience, the decision to suddenly and contrary to precedent intervene in the world's affairs without that being random occurrence would be a very good indicator. Unless Jake or Grace accidentally sent a threatening thought to all the animals, and it was the individual animal's decision, the ending of the first film would strongly imply the thought “I/we would be hurt if I don't act” to be formed and then conveyed in one way or the other, along with specific instructions of attack X, help Y. So she definitely was a character with heavily implied sapience and personhood of sorts.
Anyway, I'll admit I'd enjoy the Grace half of this possibility, Grace “becoming” Eywa is pleasing narratively. They are, well, not at odds, but certainly both Grace and the Na'vi would have never in a million years imagined such a thing was possible. The people seemed to love Grace, but they sure didn't think she was even
compatible with their world. So it's totally fitting. I like it when the story narrative decides to trolls its own characters.
But I don't think it'll happen, at least not that way. For one, that would be a serious vulnerability of the whole planet to be able to remove/extract its entire being like that. For another, I don't find it very plausible for a swap like that to be structurally possible. I don't think a planet's mind fits in a humanoid brain. And where do we go from here? Eywa/Kiri going all Zara (DIS) on us?
You
can have Grace's consciousness preserved inside like a Force-ghost manner – it
was being transferred while she was still alive in a procedure that was later revealed to preserve consciousness and memories fully intact (with some unreliable narration by Mo'at that it failed to be read), which is sufficiently different to what is assumed to happen to a dead person. That half is even supported by the film – she exhibited something that wasn't truly a memory when Kiri commuted with her. Unless that was a memory of an interaction Grace had with Sylwanin in the forest that was altered, of course. (On the other hand, it was established that the consciousness needs a congruent brain, which the trees lack, and the not-memory/memory was definitely fragmented and not Grace herself being fully aware)
It would make slightly more sense to just have Eywa finding a friend in the only or one of the few fully preserved consciousnesses like The Elysian Kingdom (SNW), or “Eywa” can also actually be made up of multiple people whom Grace now joined. That would perfectly explain why the plants like Kiri, without any magic required.
P.S. Conception through what was supposed to be a mind link to the brain during a consciousness transfer would be the thing making
least functional sense in the franchise so far. It would be totally arbitrary. The least explainable up to now would have been how the animals got the message (do Tree of Souls seeds carry information around, or do animals sleep hooked to a tree somewhere?), and how the hell did Eywa know to “choose” Jake without time travel to see the future.
Which is funny, because I did read a fan theory that Kiri is going to become Eywa in the past through time travel. About as over the top and ridiculous as you can possibly go (the author must have been watching Discovery), but it managed to elicit emotions in me because it totally fits with Eywa liking Jake and reproaching Neytiri in the first, and playing games with her own self in the second.
![Lol :lol: :lol:](/styles/flatawesome/xenforo/smilies/lol.gif)
(I'm still going with my assumption from the first time I watched Avatar – the biosphere scanned every person coming and going, the Na'vi had just never seen a newcomer on their first day before)
* Side note; who the hell was his biological mother anyway? All they said was that he was orphaned by the war, so we're to presume Quarich knocked up someone under his command?
https://james-camerons-avatar.fandom.com/wiki/Paz_Socorro