My complete roster, with commentary.
1)Mario: Duh. Confirmed already. Doc would be an unlockable costune with no special .
2)Luigi: The source of the term "Luigify," the act of de-cloning an existing character. Expect him to become a bit more different.
3)Peach: With her own Super Princess Peach game, it is possible they will change her moves around and arm her with the umbrella for most of her attacks. On the other hand, she could also stay the same. It's all up to Sakura.
4)Bowser: Mario's arch nemisis. Although slow to the point of obscenity(sp?) in melee, in Brawl they could give him more hitstun on his moves, allowing him to combo better.
5)Yoshi: Although his own platformer days are over, Yoshi will inevitably return in Brawl.
6)Wario: Confirmed in the trailer, all we know is one of his moves is a fart.
7)DK: Mario's first enemy. Well, ok, that was really his dad, Cranky, who stole the princess, but who's counting?
8)Diddy kong: Since DK's turn to the light, he's picked up a few friends. Diddy would come well equipped with peanut popguns and a Jetbarrel for recovery.
9)Captian Falcon: One of four racers that date back to the first F-Zero game. He's been in smash since the begining... they're not going to drop him now.
10)Pico: With Gannondorf moving on to have his own moveset, the slot for semi-clone of Captian Falcon is open. Pico was also one of the first 4 F-Zero racers, and he has the body mass to pull off the moves Gannondorf used in melee.
11)Fox McCloud: The leader of Team Starfox, he's been here since the beginning. Expect some changes on how the shine works.
12)Krystal: According to rumors, Fox has actually married her by Starfox Command, the upcoming DS game. Although I expect her to have her flight suit, the moveset provided by her staff in Starfox Adventures gives he a uniqueness very few can match.
13)Falco Lombari: The ace pilot of Team Starfox. Already one of the most different of the clones, it would be difficult to further separate them without losing their playstyle.
14)Wolf O'Donnel: Fox's rival, Wolf was playable in Versus mode in Starfox Assault. Expect a slow, heavy character with lots of guns and a decent recovery, thanks to the booster pack item.
15)TP Link: Revealed in the trailer, TP Link seems similar to the adult link we know and love. The Gale Boomerang could provide an interesting change, as could a wolf based dash attack, but these are hardly needed.
16)WW/PH Link: Rumored to be included, "Celda" would be the Luigified Young link. Expect a longer spin attack, and grapple hook. (not to be confused with Hookshot, which TP link uses)
17)Gannondorf: Evil warlock, wielder of the tryforce of power, bent on world conquest... if that pesky Link didn't keep stopping him. Gannondorf has long taunted us with the blade you see in his victory pose... we deserve a proper fist, blade, and magic moveset from him.
18)TP Zelda: Wielding a sword in the promo art, Zelda could have a very intereresting moveset, combining he lighning kicks with fencing-type swordplay. However, Shiek would be lost to us, as TP no longer needs the ninja.
19)Kirby: Sakura's own creation, Kirby was confirmed in the trailer, being the only character who didn't get a graphical facelift. Expect his gameplay to counter this lack.
20)Metaknight: Kirby's archrival, Metaknight was confirmed in the trailer.
21)Pikachu: Picachu can be found on anything from vitamins to airplanes, and some people even remodel their VW beatles to resemble this pokemon. Revealed at E3, nothing will keep this pokemon out of Brawl.
22)Jigglypuff: The singing wonder, Jiggs has mooved from being the joke character in the first game to being a tourny-worthy character in Melee. And of course, would the game be the same if the first thing you did was beat Classic on Very easy with 5 lives, and Jiggs DIDN'T show up?
23)Mewtwo: The ultimate genetically modified pokemon, he went on a diet just to squeeze into melee, droping from 260-odd pounds to something in the double digits. Before Brawl, he needs to put those pounds back on. I recomend McDonalds.
24)Rukario: Spelled Lucario in english, Rukario is a Legendary Fighting/Steel type pokemon who is shown throwing Ki blasts around in promo art. With his own movie and being in 4 games this fall (Diamond and Pearl, and the Mystic Dungon(?) games), his inclusion is needed.
25)Samus/Zamus: Revealed at E3, Sakura has said that under certian circomstances Samus will shed her armor and become Zero Suit Samus, sometimes refered to as Zamus.
26)Ridley: Samus's nemisis. This Cyborg Dragoness could be argued to be the leader of the space pirates, and she has been in exactly half of all the games Samus has been in, greater than any other single entity.
27)Marth: The champion must return. However, expect a nerf of his tipper.
28)Hector: Dude with an ax. Fire Emblem. Enough said.
29)Ness: Cult Classic. the Hero of Mother 2 will no doubt be back, this time stronger and heavier.
30)Pokey: Ness's nemisis, he usually uses mechs to fight with.
31)Ice Climbers: Do not doubt the power of Teamwork! Athough rumored to be dropped, this rumor was admitted to be a hoax. Retro Returneth!
32)G&W: Phear teh Sausages! This classic character also was rumored to be dropped, but there was no evidence to support this claim.
33)Pit: A third characer not seen since the NES, Pit was revealed in glorius 3D at E3. He is an angelic archer with multible jumps.
34)Issac: Representing the Golden Sun franchise, Issac is a spellcaster who uses a sword and Earth magic to defeat his foes.
35)Ray Mk I: From Custom Robo, Ray is armed to the teeth with weapons.
36)Megaman X: The second most wanted third party character in Smash. Although the similarities to Samus are remarkable, megaman could have an interesting moveset as a range specialist.
37)Snake: The one ond only 3rd party character revealed at E3, his appearence caused both supporters and detracters to repeat a classic line. Snake? SNAKE??? SNAAAAAKKKEEEE!!!!!!!
38)Sonic: Mario's ultimate archrival. The single most wanted 3rd party character for brawl. Fans have waited 15 years for this battle, and Sakura had better not make us wait another 6 more.