Mega Man is literally perfect for Smash Bros. He was made on a Nintendo console, he got big on a Nintendo console, and he fits in with the rest of the roster while standing out. Mega Man is nothing short of tailor-made for smash bros. If he was Nintendo-owned, he would have been in Smash Bros. from the get go.
In fact, I don't get why people are all over this "Nintendo owned" crap, like they're loyal to Nintendo, because Nintendo characters are good. Honestly, my definition of "Nintendo characters" includes characters that aren't Nintendo-owned but appeared predominately on Nintendo consoles, like THE BLUE BOMBER!!!
I noticed that a lot of the comments mention a Sonic x Mega Man crossover of sorts, which is probably due to the Archie comic crossover. It seems at the moment Super Smash Bros. would be the best chance at that, at least from a video game standpoint.
You think Project X Zone would have done that (which was co-produced by SEGA, Capcom, and Namco Bandai), with Sonic, Mega Man, and Pac-man, but as it stands, Smash Bros. is the best platform for that.
Pac-Man will be in the initial trailer since the Namco relationship has made him obvious. Megaman will come later like Sonic IMO. I would also like to see Rayman in my game, I think he is the third guy out after these two and whether he makes it is to be seen.
Pac-Man IMO would be better than Mega Man as a "saved for later" 3rd party character. Still, if we got both of them plus Sonic and Snake, that would be 4 huge super star 3rd party characters.