I have a few problems with that leak:
1. Megaman isn't playable. Why would the most requested character not be playable for E3? Especially since Sakurai played him last year at E3 against Mario.
2. Why isn't Bowser playable? Sure, it's a demo, but Bowser was one of the first characters for Smash 4 to be shown off with his new design. I'm sure if most recently annouced characters like Yoshi is playable, Bowser definitely should be.
3. I really doubt Nintendo/Sakurai would let everyone know how many playable characters are in the game exactly. The locks would give that away easily.
4. The format of the demo is completely different from the Brawl one. To not let people know how many characters are in the game, they just had a really small Character Select screen with a few characters. Not a bunch of locks making it obvious which series are getting more characters or not.
5. Marth is selected in the Character Select Screen. So why is he translucent? Wouldn't selected characters be solid/opaque if they're selected, like in every other Smash game, and translucent if they're just being hovered over?