Here's my take on all of the alleged characters
On Ridley, Sakurai hasn't been clear about Ridley for 1 full year. Why drag this on if the guy is just a boss? I get it if he was meant to introduce the concept of Stage bosses, but that's what Yellow Devil was used for. So with the concept already known,and us knowing he's in the game in some fashion, why not just reveal him already? He knows more people want him playable, and not a boss, he isn't afraid of deconfirming requested characters, and Ridley is amongst the most. I don't think Sakurai wants to create needless backlash if he can avoid, especially considering Nintendo wants this game to sell, you want to try your best to stay in the customer's good faith, no matter the minority, which is why they went with the quick deconfirms on all notably requested characters. Ridley has only been teased to be a boss, but why tease what's already been a precedent for almost 30 years? That'd be like teasing Mario for another Mario game, or Mario as a playable character. As its stands, Ridley has never been playable in any form thus far, that's a much more hype worthy payoff, worth the 1 year tease.
To Chorus Men, these guys were brought up for so long. They aren't particularly predictable choices, or even highly requested, so why would these oddbball characters be brought up on the Gematsu leak, which love it or hate it, has been dead on with virtually every character it listed, with the exception of Chrom, who even then it was partly right about, since he does appear as a piece of a playable character.
As for Mewtwo, Sakurai said he was considering it, sure this could mean many things. One of the possibilities i thought of was Sakurai had a pokemon slot open, and Mewtwo was probably the consolation choice if he couldn't find an appropriate pokemon from gen 6. But then again, why go back to Lucario? Its obvious more people wanted Mewtwo over Lucario, maybe so gen 1 wasn't overly represented, but again, that hasn't stopped Melee or Brawl from being overrun with gen 1 pokemon and the odd other gen pokemon. Also, Sakurai says there are 39 characters in Brawl, you only reach that number if you separate the changing moveset characters like Samus, Zelda, and Pokemon trainer. In Brawl, there was technically 6 unique pokemon characters, each character had to be developed and worked on separately. So if there can be 6 pokemon in Brawl, why lower the number? Especially considering Mewtwo was planned for Brawl anyway He was never on Sakurai's chopping board. You'd think the high demand for the character, coupled with the fact Sakurai had intended on having Mewtwo in the game, it only make sense he be a priority for pokemon reps.
Dixie Kong, she's a character that doesn't necessarily have a lot of evidence pointing to her being in the game, with the exception of her appearing on the leak with the aforementioned characters. Aside from that, she is a popular character, who would make sense to be a DK newcomer. Honestly, it makes sense for DK to have a newcomer after the success of DK Country Returns, and Tropical Freeze. We don't have all stages for the WiiU confirmed, so its posible DK gets both her and a stage. This isn't like Starfox which was a dead franchise between Brawl and Sm4sh, this series saw even more success than KI, and that has 3 reps. Thus it only makes sense to pay tribute on that success with a new character. Lastly, she was considered for Brawl but couldn't make it, due to time contraints, and if history has taught us anything, Sakurai likes to incorporate ideas he failed to incorporate on the current game to the next one. "cough" Sonic, Snake, Dedede "cough".
Last character I want to bring up is Impa, who I think is among those alleged characters for several reasons. 1, Zelda is one of Nintendo's biggest franchises, and it has had a miserable period for newcomers. The only true newcomer since Melee was Zelda and Sheik. Ganondorf is just a Captain Falcon clone and isn't accurate to his series portrayal. Toon Link is just a redesign of Young Link, who was just a clone of Link to begin with, similarly to how Link was redone in his Twilight Princess look from the OoT design he had before. So really, the Zelda franchise has been cheated on a true, wholesome newcomer for too long, and Impa can help fill that void, especially considering the only real change to the Zelda reps was a splitting of Zelda and Sheik only really. Also, her inclusion would help bring the trophy quiz full circle, because so far, it hasn't been wrong on teasing newcomers, and if Ridley is among those other characters, then it leads to her being the next character for Zelda. She's also the only other character to appear in more than one game, so she has that going for her, especially considering Skyward Sword gave her a look that would be approriate as a Smash character.
These are the characters I think are indeed coming with the WiiU, so with these 5, and the 48 other characters is what I think the planned roster was. Here's a list of characters I'd like to see become DLC down the road.
Ice Climbers(Them and the following 2 are fan favorite vets, which would make people happy to see them back)
Lucas
Wolf
Snake(Kojima can always ask Sakurai if he can make Snake a DLC character)
Ghirahim (He is an assist trophy, which means he wasn't a planned character, but they can always work on a playable model after release)
Magnus(Same principal as Ghirahim)
Chrom(He's still the main character of Awakening, and my second favorite Fire Emblem protagonist, they can always work around making someone else appear in Robin's final smash when he's playable)
Daisy( Not as her own character, but an alt for Peach, much like Alph for Olimar, seriously, missed opportunity, Sakurai)
Chrono( Wish fulfillment on my part, but I'd absolutely love to see Chrono from Chrono Trigger, as that would serve as both a Square rep, and strike a balance towards the group thst constantly request Goku)
