I don't deny that, it's clear Sakurai wants a Ninja character in the game, and really there was no one to really replace Sheik with back when Brawl came out.
But now with SS, and Impa's newfound grouth in popularity, that opportunity not only exists, but also breeds the chance of renewing the concept of the Ninja character in Smash, by adding some new moves, and specializing her by splitting her from her other half.
We probably won't see drastic changes, since Sheik was good, and for those who loved Sheik, it's likely we'll see a Sheik alt/recolor over Impa.
Did you know that Sheik was revealed and probably added to Melee before Zelda? It's probably Zelda was an afterthought, and considering that Sheik was one of the first Melee newcomers, and Sakurai's general train of thought. It's likely that Sheik was added for the sole purpose of having a Ninja character in Smash, same as IC were added for the purpose of having a Duo character.
Now the transform concept was tagged on, and not explored fully, thus needs to go since it doesn't work.
Again, seeing as Zelda seems to have a new move, it's possible and imo, likely, that Sheik has been replaced by Impa already, and Shielda split into just Zelda, and just Impa.
