I've been thinking about 'the next swordsman' and Magnus from Kid Icarus Uprising sticks out to me as probably being the most likely, though I can't help but think he might just become an even slower version of Ike.

An alternative could be Takamaru from The Mysterious Murasame Castle (perhaps a faster but weaker version of Ike) or perhaps the Sable Prince from For the Frog the Bell Tolls, who could be like Young Link/Toon Link but have the ability of transforming into both a snake or a frog, albeit it would probably be hard to execute that without making him underpowered.


Along those lines, I wonder if Link's Final Smash, (assuming they keep that concept) will involve
Phi?