Oh man, something rubs me the wrong way. like he has the face of a teenager and the body of a little kid. I don't know, his face seems off relative to the body, even in a time where big headed chibi stuff is common ground.
He has always had hair under his helmet. Look at Roll: she has always just looked like a human girl. From what I remember of early story summaries of the new cartoon, the premise isn't that he is a kid, its just that he is a robot who wants to go to school with other kids. This isn't even a new concept: it was the premise of the short-lived Dreamwave Mega Man comic.
The idea of Mega Man having a human civilian form and then transforming into his armor to fight was even present in the Mega Man Megamix manga. Mega Man is deeply rooted in Japanese superhero cartoons and TV shows. Both the Star Force and Mega Man ZX series were about ordinary humans transforming into superheroes called "Mega Man", for crying out loud. Mega Man having a transformation sequence to put on his armor is hardly outside the norms of the franchise.