Meh. I'm not a fan of Wario, let alone Waluigi. I could care less for the two.
Waluigi is an assist trophy. I'm sure he'll be usefull. As a full on character? I don't think he deserves it. Like what was stated above, Sonic is a legend. Waluigi doesn't even have his own game. If they delayed the game just to add waluigi to the roster, i would be pissed beyond all reason. If it was to add a character the majority of the people in the world knew and recognized, then ok. i can deal.
In short, i could care less about Waluigi's status in the game.