Keep in mind that in-universe Classic Ridley and Other M Ridley are identical, the change of look is purely because Other M as a whole adopts a different style, and it's clear that for smash 4 they're going to use Other M visual style (aside obviously character that are not in that game in any form to begin with, like Dark Samus).
Also, by your logic, meta ridley IS classic ridley as identity.
In addition, even ST Link and WW Link are not the same character, yet when Toon Link is on the train stage, the engine driver is Alfonzo.
But I feel that's unlikely to see Alfonzo flying around the Pyrosphere spouting fireballs when Ridley's on stage.
Also there's strong evidence that the ridley shown on the direct is a Stage Boss in the fact that was flying at constant height for too long to be a recovery or similar move.