Pichu, Roy, and Doc are all probably going to go. In fact, I garuntee it. I don't know about Shiek though. We'll have to wait until Sakurai reveals more of Zelda's movelist. I'd love to see a TP style Shiek... Ganny is also probably a shoe-in for SSBB. Although he had better get a new moveset. Despite the fact that I love him in SSBM(he's my main now, despite the whole low-mid tierness), I think that he deserves his own set(he is one of, if not the greatest videogame villian of all time).
I also hope they make Bowser better then he was in SSBM. He really sucked then, because he was just too slow, and his strengths never made up for it.
Also, Shine combos have got to go. That and laser spams are what keep Falco and Fox top tier, without them, they'd still be high. They don't need to have the best move in the game(up there with Bowser's Flying Fortress, although Bowser sucks, so that fact can be ignored) AND be freaking incredible in almost every other important aspect as well(sure, they have their share of weaknesses, but they're all overshadowed by the WTFPWNness of their strengths).
Overall, I hope that if anything, SSBB is much more balanced then SSBM. Of course, we know that it won't be as balanced as Virtua Fighter or Guilty Gear, but hopefully it'll come to the point where more then half the character list can be used competativly.