Kh1: When Soras frees KAiris heart by stabing himself with the keyblade CoM: Riku's resolution to use both light and darkness kh2: When Riku and Sora return to destiny islands 358/2 days: Xion's death BbS: All the ends of the trio DDD: the revelations of Xehanorts plans
I guess I feel my self more related to Lexaeus. Im rather silent, I prefer to listen those who are with me and speak only when I have something to say, and, yeah, I'm rather ignored in a group of people. And Lexaeus is one of my favorite characters too.
The 7 keyblades wielder will be with almost no doubt Sora, Riku, Mickie, Kairi, Lea, Ventus and Aqua.
Aqua should be the first found because she is the only one who can find the place where Ventus is.
Terra is impossible to be one of them because he is under Xehanort control.
As for the 13 darknesses... well apart of M. Xehanort, Y. Xehanort, Ansem SoD, Xemnas, Xigbar and Saix I can only especulate, but probably there will be no other member of the original Org. XIII.
Vanitas is a possibility, in fact, thinking about it, Xehanort Always make two or three backout plans for every plan he does, so it's possible that the reasson he doesn't look a bit worried when Sora is not made his last vessel is because one of his objetives was to awaken Vanitas inside the darkness of Sora, so that he can try to posess him.
The others will be probably Xehanort of other times.
Actually some time ago I did a ranking of the organizations in terms of power. Those who have a power level similar are ranked the same and who is the more powerfull between them may depend of the circunstances: 1º Xemnas 2º Dualwelding Roxas 3º Lexaeus / Xaldin 4º Xigbar / Marluxia / Saix 5º Larxene / Axel / Demyx / Zexion (with time of preparation and a plan) 6º Roxas / Xion 7º Vexen / Luxord 8º Zexion
In the case of Zexion, obviously any other member with time of preparation and a plan have more chances of wining, but it's the way Zexion fights, so there it is.