I don't see Falcon's being changed unless they really wanna cash in on the memes and reference THAT anime scene. Otherwise the current one already works perfectly.
Diddy, Lucario, Peach and Yoshi need to be changed due to how FSs work now. Diddy and Yoshi I believe will keep the same concept kinda like what they did to Giga Bowser but streamline them.
Lucario is gonna get Aura Storm back and transform into Mega Lucario. You can't change my mind.
No ****ing idea what they can do with Peach but if Geno happens to be in I could see a Mario RPG reference.
Luigi, Meta Knight, ROB and WFT can be expected to remain the same, I see no reason to change them(other than Luigi's Poltergust design, that is).
Robin needs a new one due to Chrom so I hope they keep Pair Up but have him team up with Morgan because that would be adorable.
Young Link is either gonna be Fierce Diety or Triforce Slash feat. Fierce Diety
Have we seen Dr Mario's? Is it seriously still the awful Smash 4 one?
Yeah