We'll find out in Kingdom Hearts Ultimix Collection Vol 3, where what work was done will be stitched together into a 6-hour long movie.

It'll probably be reworked into another game, especially if Nomura has anything to say about it. Dude refuses so hard to let go of Versus XIII that he found a way to put it into KH3 and likely 4.

I mean, why not? Nobody can understand it anyway.