Actually, some of the official FFXI books released over in Japan point towards Atomos and Phoenix being our next two avatars. A good friend of mine owns one that offers a detailed and comprehensive guide to basically everything in the game (NPC backgrounds, the other areas of Vana'diel yet to be released, etc), and in the Avatar section, which details everything regarding our current Avatars, both Atomos and Phoenix have their own small sections in there. Odin and Alexander are mentioned as storyline characters, and didn't appear in the same section as the other ones.
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