Honestly I never knew people where thinking Mega Man was a possibility for Brawl? Well, I am sorry to break the hopes of those who did. Acording to Keiji Inafune, creator of Mega Man, Mega Man will not be in Brawl:

Well, I really do love Super Smash Brothers. It’s a great series…but, Nintendo hasn’t asked me yet if they can use Mega Man in their game. I’m still waiting…we have a little bit of time left, it’s not coming out for another few months. They might get around to asking us if we’d like to put Mega Man in Super Smash Brothers. Maybe if somebody from Nintendo is listening to this podcast, they’ll give me a call.