I know, once I saw someone post a photoshopped picture of Terra with white hair, tan skin and yellow eyes, i was convinced he was Xehanort. I didn't realize he'd be possessed by MX though, i thought that he'd severely rely on darkness and it would result in a change in appearance and memory loss.
Well, the game IS supposed to bring everything together, and having Xemnas with the wayfinder would explain things.
Idk if Xemnas would be talking about Terra though, but I'm definitely wondering if he really meant Ventus. Just like when he said "I'm what's left. Or, maybe I'm all there ever was."
Hahaha I know, Riku's definitely confused on how Ansem's still around though.
See, I'd like to think Terra was in control, but he couldn't have control of the body most of the time considering the experiments. I feel like although it's possible Terra overtook the body towards the end of the experiments (why else would Apprentice Xehanort attack Braig?), I think MX was the major influence.
By the way, I just realized... young Master Xehanort probably is the Mysterious Figure. I feel like this incarnation doesn't have the ability to wield a Keyblade yet and is going to use the blue ethereal blades against Sora and Riku.