http://boards.4chan.org/v/thread/423318271
I have a friend on the Bandai development team who provided me with some information regarding new playable characters. As many of you with development experience will understand, he's working under contract and signed a non-disclosure agreement, so he could get in legitimate trouble if I shared his name (or mine, and they trace the leak to him). It's irrelevant whether or not you believe this; makes no difference to me. He claims it's true and that these will be gradually revealed via official announcements, intentional leaks (apparently that's a thing), and of course fully proven upon release.
There will be 9 new playable fighters (including Ridley and Inkling). Simon Belmont, King K Rool, Geno, and Skull Kid were chosen based on the sm4sh dlc poll results. Also, there will be a new playable pokemon, and 2 more characters still under development which he personally doesn't know who they are yet (or won't tell me anyway).
Also, there will be echo fighters for the following characters: Sonic, Ike, Donkey Kong, Diddy Kong, Mario, Samus, Sheik, Inkling, Little Mac, and Captain Falcon. That's 13, counting Peach, Lucina, and Dark Pit, which were already confirmed. Echo fighters always come from the same universe as the original fighter, and have the same moveset as the original, but with some different properties, effects, animations, range, and power/speed balance. Obviously they’re way easier to include than new fighters.
He claims there will be 2-3 more dlc characters and echos released a few months post-release, to sustain sales.