But that doesn't mean the policy of remixing a roster isn't unusual for the genre, nor is it necessary something that should be avoided. I don't think it's fair to expect the same roster to return over and over again with the only changes simply expanding it. New games do not make the old games obsolete, and I don't think it's right to view Smash as singular title routinely evolving and expanding. Not only is that boring, but it's an unfair pressure to place on the developers, when the reality is they're not going to be able to continue expanding the roster forever without hitting absurd development costs.
It's not even Smash in question here, it's more or less every single franchise that have ever existed. Items are removed and replaced in The Legend of Zelda. The pool of power-ups in Super Mario Bros. constantly changers. Every fighting game series has a mixed roster from title to title. And even though working with established characters from Smash should be less work than a new character, it's still work. Work that may, should the developers feel it, be better spent on establishing someone new.
End of the day, at least for me, part of the excitement of a Smash game is not playing that character I loved a game or two ago all over again as I have done so before. It's trying new characters and seeing what they'll bring to the formula. Captain Falcon is one of my favourite characters in the roster, but playing as him in Brawl still evoked similar feelings to playing as him in Melee and 64 (timings, speed, and damage aside). Meanwhile playing as Snake, Metal Knight, Pokemon Trainer, and Pit was a totally refreshing experience. Same goes for playing Peach, Bowser, Zelda/Sheik, and Mewtwo in Melee. And this is what I'm excited about for Wii Fit Trainer and Villager.
Maybe Sakurai and co have a different policy, but I don't know. Brawl cut Roy, Pichu, Mewtwo, and Dr. Mario. Granted, Dr Mario and Pichu were clones, Roy to a smaller degree, and Mewtwo the only totally unique moveset. But still, it would not surprise me to see a small portion of the roster cut for Smash 4, or at the very least massive redesigns made to some clones. Do we really need Fox, Falco, and Wolf to return at the expense of a new character? I love playing as Falco, but I've played him for three games, and if cutting Falco and Wolf to keep Fox as the only one with that moveset rewards with two totally new characters, I'd take it.
Toon Link and Luigi kind of throw a spanner in the "cut clones" theory. Luigi less so.