Dream Drop Distance Red Eyed Unknown (Warning: Possible Spoilers)

Okay. Here's the warning. I'm pretty sure a lot of people have figured this out by now but I still have a question.

Spoiler

The red-eyed creature that Riku fights in DDD is Vanitas. Right ? Or some form of Unversed. Because Vanitas, before Sora was born, was described as a "humanoid creature with red eyes and similar in appearance to a Heartless. After Sora was born and Ven felt him, Vanitas took the physical form of a "dark version" of Sora.

If the red-eyed creature really is Vanitas, does that mean he will return for the battle between the seven keyblade wielders and the 13 darkness people ? Will he be revived and make another appearance ?

I read somewhere that Nomura said in Kingdom Hearts, no one truly disappears or dies forever, and that there's always a way to revive them. They didn't give a source though, they just stated "Nomura said" if I remember correctly.

There's so many theories. My main question: If Vanitas is the red eyed, and he made a recent appearane as the original red-eyed form AND a few seconds of his final "dark-looking Sora" form (as we see in the trailer), does that give any clues that he will be returning for a spot in the final battle with the Xehanorts vs the light ?

Sorry if I didnt give enough information to make an evaluation yet. Thank you.