I agree with basically all of your comment up until this point. It's a case of correlation not necessarily equaling causation if K. Rool misses out on Smash after not appearing in Returns, given that characters like Luigi, Ganondorf, Marth, Diddy have become playable despite not appearing in key games before their newcomer debuts, and the practice of adding characters unknown to the younger generation through retro and shock characters has existed since Melee. Kind of like Ridley not appearing wouldn't be due to him being "too big" or Little Mac not appearing wouldn't be due to him "having no potential," K. Rool not appearing wouldn't be due to some arbitrarily high quota for new game appearances applied specifically to him; for all we know, Sakurai might just prefer Dixie, or be dense enough to not find K. Rool unique like that one almost-certainly false leak suggested.If Dixie gets in SSB4 over K. Rool, it will be because K. Rool hasn't appeared (to our knowledge) in the "Donkey Kong Country Returns" series. For what it's worth, it is entirely possible (and maybe probable) that Dixie is a more well-known character to the younger generation because of spin-off appearances. And maybe that's worth a lot. But I don't think it lessens K. Rool as a character.
Toon Zelda's "competition" is, what, Ghirahim, a one-shot, and Tingle? If there's a newcomer from the Zelda series, it would be her, although the fact that people aren't collectively fangasming over her for being planned for Brawl and being in Wind Waker HD is a testament to how little fanfare there'd be if she were actually added.