Ok this is what I think.
First when Nomura means "curve-ball"/"fastball" I think he means something that we would not expect (DUH) we already know this and what would be more unexpected than KH3 I think we all remember that he said production for KH3 wouldn't happen until Versus XIII was finished. Story wise I think we are there because (SPOILERS STOP READING IF YOU DON'T WANT SPOILERS FOR 3D) Xehanort and his other Co-Norts (see what I did there
) are ready so that takes care of the XIII Darkness-es and the VII Lights are almost ready because so far we have Riku, Sora, Kairi, Roxas, Lea, Aqua, Ven, and I don't know about Terra since his fight with Xehanort he's gone MIA. (END OF SPOILERS) Plus look at the secret message for 3D and if you look in the credit you can see where Sora and Riku are about to go into the light that it forms a III. Another possibility is a Final Mix Collection and maybe he's somehow going to get the other games like BBS, re:C, 358/2, and maybe even 3D into HD somehow.
Really I think we are just going to have to wait till E3 I think Nomura being the troll he is, is hiding something KH related and it won't be announced until then so cross your fingers.