Fun fact time! For this game (Super Smash Bros. for 3DS/Wii U, of course), Sakurai has never shown us part of or all of a newcomer's fighter model prior to their official reveal. We saw part of Ridley's tail, and a bunch of his shadow. So we've seen part of him. As for Palutena and Miis, we've seen them as statues and stage characters respectively, but those parts of certain stages, and are not fighter models.
So, as I was saying, there's some consistency to be had here. And with that pattern in mind, it's easy to deduce that Ridley is not a playable character. Unless he is in fact playable, of course, in which case he will be the character to break the pattern. So I'll state my statement again because it rocks and it's a consistent pattern to base claims off of.
For this game, Sakurai has never shown us part of or all of a newcomer's fighter model before their official reveal.