It's Smash world, party time, excellent! Smash world could have been the old name for Smash run? Remember, the Wii U and 3DS were build at the same time, but separately. I wouldn't take the sound files you hear in one to be in the other.
I will not be surprised if this leak is fake, but I still believe to be true, because of what I said before: They need to pull people to buy this game. The common player will not buy this game and a Wii U just for the same game again. They need ALOT of stuff different, and also need stuff people really want. More characters is what people want. And having some being unlocked buy having both games is the best way to do that.
Regardless, I think this game is getting DLC. No doubt about that. Not just because they found proof for DLC pages on the 3DS, but also with Mario kart 8 and Hyrule warriors. Nintendo is starting to do DLC, but they are planning for the long term un both of those games. I can see the same happening here. Sakurai, or the team, may make characters and stages for this game for YEARS, if they want to keep this game relevent, and not want to release a new version for a long time. Skullgirls shows that you can keep a game exciting with a new character every 2-3 months, I can see that happening in smash as well, and laster for a year or so.