Anyway, what characters would you consider likely to be dropped?
I'd say Ike is in the deepest ****.
Lucario is the most likely I would say, but I would put either Toon Link or Ike as the second-most likely character to be cut.
Overall, here are the characters I think have a probability of being cut and the brief reasoning for each of them:
Lucario:
Primarily placed in to represent Diamond/Pearl, his time in the spotlight is now gone, and most of his popularity with it. Will likely be replaced with a new "flavor of the month" Pokemon in Smash 4.
Ike:
Primarily placed in to represent the Tellius arc in Fire Emblem (FE9/FE10). FE9/FE10 were among the poorest selling games in the series in Japan. The Tellius arc will likely not be revisited for this reason. If cut, Ike will likely be replaced with the most recent Fire Emblem lord at the time of development.
Toon Link:
Primarily placed in because he was the "newer" Young Link and was still receiving games at the time of Brawl's development. Since Toon Link will be going into "retirement" according to Auonoma, and Young Link's games are being remade, its quite possible Toon Link will be swapped for Young Link, or an entirely new Zelda character will be placed in.
Wolf:
Krystal's fans are whining that she deserves a spot. However, Star Fox certainly does not deserve four slots. There is a good chance that if Krystal does get in, it will involve Wolf getting axed.
Snake:
Primarily placed in due to a personal friendship between Sakurai and Metal Gear creator Hideo Kojima. If Sakurai does not return to direct, there is a good chance that Snake will be axed seeing as his inclusion was basically a personal favor. Also, we do not know Sakurai's or the Smash Bros. series' policy regarding "guests". In most fighting series, "guests" are dropped in the next game and usually never return.
Sonic:
See the latter explanation for Snake. We do not know Sakurai's or the Smash Bros. series' policy regarding "guests". In most fighting series, "guests" are dropped in the next game and usually never return.
Squirtle:
Pokemon Trainer may be dropped since so many characters are needed to be programmed for his slot. Also, there is the possibility that Game Freak, whom has a heavy hand in determining Pokemon content for Smash Bros, will want for the Pokemon Trainer to have Pokemon from another generation, thereby axing PT's current Pokemon.
Ivysaur:
Pokemon Trainer may be dropped since so many characters are needed to be programmed for his slot. Also, there is the possibility that Game Freak, whom has a heavy hand in determining Pokemon content for Smash Bros, will want for the Pokemon Trainer to have Pokemon from another generation, thereby axing PT's current Pokemon.
Charizard:
Pokemon Trainer may be dropped since so many characters are needed to be programmed for his slot. Also, there is the possibility that Game Freak, whom has a heavy hand in determining Pokemon content for Smash Bros, will want for the Pokemon Trainer to have Pokemon from another generation, thereby axing PT's current Pokemon.
Lucas:
A luigified-clone that is less popular than the original. The Mother series is finished, and two of its three games are Japan-only. Sakurai may opt to cut Lucas if space for the next Smash Bros. is limited considering that Lucas represents a dead series that is mostly Japan-only and the character itself is among the least popular newcomers introduced in Brawl.
ROB:
The reaction to ROB was about the same as it was to Dr. Mario, Pichu, and Young Link in Melee. ROB also the only character series not represented with a stage. ROB might have been placed in Brawl as plot device for the SSE. ROB is less likely to be cut than the other characters mentioned thus far, however, keep in mind that ROB was among the few Mario Kart racer veterans not to have been playable in Mario Kart Wii.
Note this list is not about characters that are "likely" to be cut, but rather characters whom are plausible to be put on the "chopping block". The Brawl newcomers whom have almost no chance of facing the chopping block are Wario, Diddy Kong, Meta Knight, King Dedede, Zero Suit Samus, Pit, and Olimar.