I wonder if the development team will be as ambitious about the music as Brawl was. Werent there over 300 songs? I just can't ever imagine that kind of thing happening again on an equal or greater level. Some amazing songs came out of that game, that Tetris A them was epic.
Well if Sakurai is still in charge which I'd imagine he is, it should since it was his idea to get over 30 different composers to compose the music which lead to such an amazing amount of song with great variety. I'd imagine he would want to do the same thing for the next Smash Bros as well.
I don't know if anyone remembers but the game code containing Plusle and Minum as team characters, Toon Zelda/Shiek, Dixie Kong, and Mewtwo were in the game. I really wouldn't mind a representative from more generations of pokemon than the 1st and last, but double teaming electric mice sound like double Pikachu's and if they do get placed into the game I hope its not at the cost of another completely new character. Same goes for Toon Zelda, there has got to be more deserving characters that are not Link or Zelda in any human form.
The only character from Brawls code that I think stand a chance of being in the next Smash Bros is Dixie Kong and Toon Zelda. Any new Pokemon will be from the most recent one Black and White, so I doubt they'd still use Plusle and Minum. I doubt Mewtwo will return since Lucario pretty much took his spot and Lucario will more then likely be replaced by Zoroark. If Mewtwo was to return, then they'd also have to keep Lucario as well as add Zoroark. Plus since I'd imagine they might want to add a Female Pokemon Trainer who uses more modern Pokemon, I think Mewtwo and Lucario will both be gone too make sure Pokemon doesn't completely dominate the number of playable characters.
If they use Toon Zelda though, I'd hope they don't use Toon Shiek and instead make her transform into a Phantom from Spirit Tracks. Anyone who's played Spirit Tracks would know that all the different Phantom armors that Zelda's spirit can posses in that game would offer a wide variety of movesets to use. That would be a good way to differ Toon Zelda from normal Zelda. Normal Zelda transforms into a fast and agile character, while Toon Zelda would transform into a slow and powerful character.
As for Ridley, all he needs to be is a Charizard that is slightly bigger. Bowser is huge in Brawl and I don't see why Ridley couldn't be that size with wings folded.
I easily expect Ridley to be playable in the next Smash Bros. Since he was one of Brawl's most requested characters that didn't become playabe, this pretty much guarantees he'll be playable in the next Smash Bros. In comparison, Wario, King Dedede, Pokemon Trainer, Meta Knight and Diddy Kong were the most requested Melee characters that didn't make it into that game and they all became playable in the next Smash Bros. So I'd say Ridley's chances are pretty good this time.