Sakurai just doesn't seem the type to heavily change movesets like that. See Ganondorf, who under almost any other developer would have gotten revamped after his rushed clone appearance in Melee, but that firmly stuck as the basis of his character going forward even as he got new attacks/animations. I think it will be closer to another Brawl/Wii U type game, where some characters are lost, but the game is overall clearly building up on the previous one rather than something new from the ground up.