On the topic of the final FE roster for Brawl, I've got mixed feelings myself. I'm beginning to doubt that we'll get three FE characters after all. Most of the supposed "leaks" we've gotten in the past month have indicated a total roster in the neighborhood of 35 characters, lower than I was expecting, and I can't help but worry that somewhere along the line, as we get closer and closer to the release, one of them was/will be the real deal. Doing the math adding the characters that seem most likely to be in with a limit of 35 tends to leave no room for a third FE rep.
Discarding that though, presuming our previous logic that gives us a roster closer to 40 turns out to be true, my expectations are obviously Ike and Marth as the first two, and a third who is pretty much up in the air. I'd absolutely expect it to be one of the Lords - they're obviously the most popular and important characters in their games, and so the best choices. I'd break it down like this:
Celica/Alm/Eirika/Ephraim - As Sonic Wave said before, these four can be discarded outright due to coming from the least popular games in the series.
Elincia(/Sanaki/Tibarn if you count them) - Also probably can be disregarded due to being secondary Lord(s) in a single game, very much so eclipsed by Micaiah and Ike.
Celice - Eclipsed by his father, and in both abilities and appearance very little different from him anyway. Theres no reason to take him over Sigurd, and no reason to take him if Sigurd is rejected.
Hector - Very much so doubt it. Lyn was more popular internationally, and only made AT. Neither is well liked in Japan from what I've heard, so he has no help there. I'm expecting AT at most.
Micaiah - Since FE 10 was not overly well received in Japan and only just got released in the US, I don't see her getting in on popularity. Her only hope from what I can tell is if she was pre-decided to be a Radiant Dawn add and Sakurai doesn't decide to take her out now that the delay made such a near-futile gesture. Or if Sakurai is just that desperate for variety, but then again there are other options in that department too. I wouldn't write her off, but the more I think of her situation, the less optimistic I become about it.
Sigurd - Distinctly possible for well-known reasons, but has two problems. First, hes Japan-only, with no known plans for a potential international release of his game. Second, that white w/ blue cape outfit Ike has may very well be intended to resemble him, in which case he clearly didn't make the cut. I'm quite curious as to what his ultimate fate will be in Brawl.
Eliwood - Don't honestly expect him myself, but its possible Sakurai could see him as a kind of compromise between the international fans who were clambering for Lyn and/or Hector (since hes from the same game as them) and the Melee fans who want Roy back (since, being Roy's father, he'd be pretty similar to him in-game). Also, if Chronobound's information is accurate, hes the only GBA Lord who isn't disliked in Japan, which, while not necessarily meaning much, is something.
Leaf - He may surprise us. If what I've heard is right, though he only starred in FE 5, he was also in FE 4 as a member of Celice's army, making him a multi-game character. FE 4 and 5 are also the most beloved amongst many Japanese and "hardcore" international fans, which helps him. He also has the variety thing going for him if what I've heard is accurate, since promoted he can use any weapon or magic save light and dark. Without knowing details about his popularity or role in FE 4, I can't be sure of any analysis, but I wouldn't write him off. His chief obstacles are Sigurd and being Japan-only from what I can tell.
Roy - Very unlikely since he is not well liked by Fire Emblem fans anywhere, but if Sakurai decides to give in to his Melee fans he may just make it back. I'd put him as the least likely realistic possibility.
Zevox