They go in order of 64, Melee, then Brawl...
GET WITH THE PROGRAM PEOPLE
^ well, to some degree.
1.At E3 2006, Mario, Link, Pikachu, Kirby, and Samus were confirmed in the first trailer. They were all starters in SSB64 AND MELEE. Then of course they added 5 newcomers [Meta Knight, Pit, Zero Suit Samus, Wario, and Solid f***ing Snake], and in the Nintendo Space World 2006 Trailer. Then, Zelda was randomly confirmed, followed by Bowser. Then, at Nintendo's E3 2007 Press Conference, Donkey Kong ws confirmed, and Yoshi shortly after. That's the original 8 starters from Melee, along with Zelda and Bowser. Next came Peach, and the somewat shocker the Ice Climbers. [Not even gonna go there] We're only missing 3 Melee starters: Shiek, Captain Falcon, and Ness.
Now for them, it comes down to this. As we all know [hopefully], Captain Falcon and Ness were unlockable characters in SSB64, and starters in Melee. Therefore I conclude, that if Shiek is going to be playable in Brawl, there is a strong chance she won't be playable if Captain Falcon or Ness IMO. Minus any possible newcomers [as all confirmed characters are on the site as of NOW], if Shiek is in Brawl, Captain Falcon and Ness will follw. Then...it's anybody's guess. But I imagine if Sonic or Megaman are in Brawl, Sakurai will save them for "the end". And I think that could be some big gaming event, like E for All, or something. Or even Nintendo Space World 2007 [again], even, since we got the 2nd Brawl trailer then, and I think we got one or two Melee trailers there. Definitely keep a look out for E for All and Nintendo Space World 2007 folks.
As for this icon theory... "Quite frankley dear, I don't give a ****."
^ I use evidence, popularity, and the other 6 or 7 big points of mine to judge a character's chances in Brawl. I don't care about this stupid theory. It's just a guess, that's all. Who cares IF YOU WERE RIGHT, everyone was guessing Snake, Krystal, Captain Falcon, King Dedede, or Lucario anyways. >_<