To be honest, that's actually a theory a lot of people have.I even remember someone saying that would explain some of Cinder's more vulnerable and scared moments in Vol. 4; it's really Pyrrha channeled through Cinder's body. Plus, with what happened to Ozpin, it's possible (I don't fully count it, but it does show some possibility). Though am I the only one who might see a scarier/sadder side to this if it turns out to be true in the official release...Regardless to be honest, if the writers are willing (or even planning) to bring Pyrrha back into the main story (and not just keep her dead and/or have her resurrected as a part of the "Grand Finale's Victory), I can see this as one of the best ways--at least as a first step.