I believe that Sakurai did play on everyone's expectations about Mewtwo. I don't know if it was hint or not specifically but I still think Mewtwo will be playable. I say this because if you think back to Brawl we had six different playable pokemon. Then if you believe in the forbidden seven (mewtwo and minun & plusle) it was suppose to be 8 (9 if you count minun and plusle as two different characters). So if Sakurai was willing to have 8 playable pokemon, and we only know about 4 so far, I highly doubt Mewtwo won't return..at least I hope :S
Pretty much. I think people really fail to realize that Sakurai and Sora have the full hands of Namco on their side. As you can see, development has sped by at an awesome rate and a lot of content is being packed in. Its not hard to imagine that this iteration of Smash will be a packed roster of characters. If Brawl had 39, I have no problems picturing 50+ roster for these titles.
Welcome to Smash 4 AKA Marvel Vs Smashcom 2 : Electric Boogaloo
Tldr : there's going to be a big ass roster since namco is helping