Let me be clear, I have nothing against Rayman making it into Smash, but NO character will fill that void. To say that Sonic and Mega Man can't fill that void but Rayman can is just bias talking at that point. I mean if those two can't, no one can.
As it is now, and despite what people may say, there aren't really any other characters on the same level as the three already included, at least in terms of being iconic and having ties with Nintendo. Maybe Bomberman, but he has his own problems as it stands. Maybe Banjo, but not in the same way. That's not to say we can't get more, but including Rayman would hardly fill the void, it would just increase it to include the tier of third-party candidates Rayman occupies.