Okay, I didn't read all the previous posts, (I did read the two HUGE theory posts...well, most of the second, but all of yours tyler) but I'm gonna try to address what issues I can remember.
Okay, Master of Keyblade: I think he's probably the one who made the keyblade/s. I think he at least made the first one probably. No theorys on why really.
Chasers: I don't know much about the chasers. I think they re the armored people. SOme kind of Keyblade collectors maybe. you know, someone who Chases Keyblades. I wonder if there is some way to override a keyblade's free willl, and wield it without it choosing you? I udnno, maybe. Oh, and the person in a cloak coming towards them, he must be their enemy, they look up when he comes, and while you can't see their faces, they look surprised, kinda in the scared way. Which means, they are good guys, or he is a good guy. I really don't know which would be which. To me, they all look like they would be bad guys, buit if they're against each other...I dunno. I guess the cloaked guy would be more likely a good guy. For one, he's just one guy, usually their are more bad guys than good, and for another, maybe he was like mickey, trying to be secretive with his cloak. Oh well, this leaves a lot of speculation.
Four Realms: Something I considered during readcing the two big posts, when the worlds were all connected, were the realms connected too? I mean, if they were, it's quite possible they were like seperate large nations in the whole world (I mean whole world as in not seperatd) and might have gone to war cause of that.
Kairi Wielding (don't take that the wrong way): I think it was Riku's key splitting like when Sora and Roxas dual wield too. I mean, as far as we know, there are no female key wielders, and if the keys were created a long time ago, it's likely they aren't usable by women, Cause, in old times, women never fought in wars. Now, you girls reading this, I'm not saying we're better. Just don't complain at me.
Keyblade War: I think that the one it talks about would be one in the future, but there could be both one in the fututre, and a past one. Quitel ikely. You know, if Kairi's grandmother cna remember connected worlds (which it seemed she may have) then, maybe some of the people who started the war could still be alive, after all, the kids were the ones that saved the world/s from total destruction.
*Whew* (This is hard).
Birth By Sleep: This HAS to have something to do with Sora's time in Namine's capsule. He was being reborn by sleep. I have considered (briefly) that it could be the dirty meaning, but as its a kid game, I HIGHLY doubt it. Sora was after all in that thing for around a year, a lot can happen in that time. Maybe even a short war.
As for that thing that the armored guy stands on: I think it might be some sort of something he can summon. WHich would explain why, hen he dismisses it, it might dissolve like that. But there's no telling.
One more thing: My friend brought up something today. It has nothing to do with the extra movie, but do you think Riku could have a nobody? I mean, he was taken over by Xehanort's Heartless, whcih could mean he was a heartless, which would mean he has a nobody. If that's true, my guesses wold be 1. Hayner or 2. Seipher. Although I doubt Sepher.
Ok, that's all I can think of (and my hands are tired) but I'll be checking back here. Nice theorys though Tyler and...ok, I forget your name, guy with the heart avvie, the second huge post. Feel free to PM me and disscuss it there. I love disscussing KH mysterys. So, OUT! (No, I never say that in real life)