First of all, I have to say two things: This is an opinion made with no experience of the game besides the Demo (which obviously doesn’t have Little Mac), and second, Little Mac is my favorite newcomer to the franchise.
Now, with that said, I was astonished by Lil’ Mac’s playstyle when gameplays of the game appeared, his speed, his damage, his special K.O. ability, he looked like the perfect character, but there is a blatant fault to balance him out, he is worthless mid-air, and when he is launched out of the stage, his side special and up special don’t really help him get back. Still, people are complaining everywhere about how “Overpowered” he is, and, it may sound harsh, but those are complains from people who don’t know how to deal with him, don’t try to experiment or get better to counter the character, and specially when Little Mac’s main weakness are grabs, a move that most of the beginners to the game don’t use.
I won’t say it is easy, dealing with a skilled Little Mac player can end up in defeat pretty quickly, I’m going to use a boxing ideology to this: to win against a foe, you have to make him fight on your terms, this applies to Super Smash Bros too. When Mac is on the edges of the stage, that’s the moment you have to exploit his weakness, normally they would stay on the center of the stage to avoid it, and here is when grabs come in handy, throwing him repeatedly off the stage, and then hitting him can be a secure KO for you, specially if you have heavy hitting projectiles like King DeDeDe’s spikes, Duck Hunt Dog’s can or even a kicked fire hydrant from Pac-Man. I’ve seen several replays on youtube when even skilled Little Mac’s player lose pathetically because their opponent knew how to exploit his weakness, those videos normally went “Game starts, player A doesn’t moves from his side of the stage, Little Mac dashes and punches, player A dodges or blocks, then grabs and throws Mac off the stage, when he tries to get back, player A hits or throws him of the stage, rinse and repeat until KO”.
I don’t really think Nintendo is going to balance him, specially with such a huge weakness, maybe they’ll just shave off some damage points to his attack to try and listen to the players, but that would be it. I’m against any nerfing done to him, he requires skill to play him right, and it requires skill to defeat him, just like any other character in the game or in any other fighting game.