As much as I want Skull Kid, I'm afraid he won't be in base, and maybe not DLC due to how the Zelda characters are handled.
However, if there's another ballot, I'm gonna make a lot of votes for him. I can't see him being a boss, because even if they decide to do a fighter-sized yet unplayable boss for once, it'd make more sense to make him playable as well because, as I pointed out, he's fighter-sized and so he'd be easy to animate as a fighter, and he's never actually been a boss until Twilight Princess (in which he's more of a miniboss that you barely fight, it's more-or-less a game of Tag while you slash through his puppets) and Hyrule Warriors (in which he's also playable).
Vergeben says Ken and Icineroar are left.
He's never claimed he knew who's left; plus, there's also the SE rep (who may be DLC but still).