Sakurai recently tweeted to Masuda that he had no idea about Pokemon gen 6, and pretty much anything newly related to Pokemon. This means that nothing in Sakurai's initial document for Smash Wii/3ds involved any of the new pokemon stuff that has been announced recently. This includes Mewtwo's "revival" as well.
I think it's safe to say... if Sakurai wants to include gen 6 stuff, this game will be delayed and take even longer to be released. Modeling, and programming new pokemon into this game is just going to take up more time. I hope they ignore it completely and maybe leave it for DLC or something.
You're misconstruing what Sakurai said and putting words in his mouth. All he said to Masuda was that he looked forward to seeing more of Pokemon X and Y at E3. He may or may not already have Gen VI designs and concepts available to him for use in Smash Bros., but there's no way to know.
However, now that it's apparent that Gen VI won't have a "mascot" Pokemon, I too would rather just have Brawl's Pokemon roster + Mewtwo. None of Gen V's Pokemon made a big splash like Lucario, who has been the most successful Pokemon of recent times. It continues to make prominent appearances in the Pokemon games and anime. Its aura mechanics let it stand out in Brawl, and it would be a shame for Lucario to be replaced by a random Pokemon from Gen VI.
Replacing Lucario with a Gen VI Pokemon without a prominent role would be like if Brawl had Garchomp instead of Lucario... --- [Este mensaje fue borrado al deseo del dueno]