Ok I figured how to comment here so I'll just paste what I wrote on twitter:
Marluxia, in japanese, specifically states that he's in the True (New) Organization XIII. His comment in english is very ambiguous and confusing, but it's implying that he knew the organization's true purpose all along, not that he aligns with the former Organization XIII.
Also:
"One thing I noticed from the trailer is that, as they are getting ready to launch off, Buzz's lips move as if he's saying something, but there is no dialogue."
This also happens in the Mike Wizowski attack and they indeed say things in the japanese trailer, but were muted in the english one for some reason or another (maybe so they didn't need to subtitle it?).
And finally, Riku and Mickey never lost their memories of Castle Oblivion, so he definitely remembers Riku-Replica, though that still doesn't confirm him.
Still, great analysis!
