I don't know. They haven't announced it yet
In all seriousness though, I'm not making the argument that it's something else, just pointing out that there's room for interpretation there, so don't get too excited until you see something more official. The two red flags to me is him casually dropping that there would be an expansion for the game before he was actually supposed to announce it. I feel like corporate SE wouldn't be a fan of that and I've always had Tabata pegged as a company guy. And second, because he's talking about extended FFXV content in the first sentence, so it seems strange to refer to an expansion in the same paragraph.
As for what he's working on, who knows. Could well be that he's done with the brunt of the work for FFXV, just overseeing the DLC content while SE has him assigned to a new project. Could be FFXV. Could be an expansion for Type-0 or something, I dunno.