I find it's easier to keep a strict policy of belief. Unless Nintendo says it, or many major gaming news companies say it's confirmed, I'm inclined not to believe it.
I've been wrong before, but...
Seeing as how our good friend Masahiro Sakurai posted on his own blog that there wouldn't be a new character and such, I'm once again inclined to not believe it.
On another note, I doubt Sonic or Mega Man are going to be playable. Highly doubt it. For the record, I also do think that Zero Suit Samus is rather kickass--screw all that think otherwise.