I don't know. I guess they aren't popular enough compared to Charizard, who could even suppress Mewtwo in popularity. Plus, I'm not sure how many people liked the Pokemon Trainer gimmick. I mean I think it's unique, but I don't use Trainer like at all. Someone else can probably explain better than me, though. I just am not a fan of Squirtle and Ivysaur for whatever reason.
I loved the transformation mechanics for Zelda and the Trainer. True, I always played Zelda alone, so Shiek got very little game time, but the Trainer I played all three equally. I liked Squirtle the best, but because of the stamina mechanic and the fact that it auto-rotated the characters, all of them got a go. I really miss that. My team in HG/SS even was based around Squirtle, Ivysaur, and Charizard.
I would hope that more DLC is coming, and that they give us Brawl vets. Didn't Sakurai say that he hated cuts from the roster? With DLC, there's no base to the 'X has too many reps' arguments, so I'd be OK with most characters returning. Also, it seems easy enough to insert new DLC characters into the game.
My list is
, since I used them all pretty heavily in Brawl. I never really got into Lucas that much since I'm terrible with Ness, but I wouldn't be opposed to him.
And I'd love to see some promotions. Yeah, I'm still wishing Ridley made it playable, but I'd also like to see some Assist Trophies make the jump (Midna, Ghirahim?). It's DLC, so they don't need to care so much about infuriating fanbases (though why anyone would refuse to buy the game because of one character's inclusion is beyond me...aren't there 48 other characters you don't loathe?) or having even representation among series. And Smash DLC would be a great way to hype other series - Fire Emblem was a Japan only thing until Marth showed up in Melee.
...now if only Hyrule Warriors had come out later and they used those outfits and movesets to hype it...
I'm betting DLC is on its way, and I hope Wolf is one of the first coming. And it would be great to see rehashed stages as DLC too - Great Bay or Saffron City, anyone?