What is Hideo Kojima up to?

What is going on with Hideo Kojima at this point is anyone's guess, but an interview at MetalGearSolid.be with Donna Burke, who sang "Heaven's Divide" on Metal Gear Solid V: The Phantom Pain, might reveal a interesting albeit small nugget of information. She says that she's still in touch with Hideo and is curious about what he's doing next:

"I'm very interested, curious and excited to see what Hideo Kojima is going to be creating next. I've heard he will still be based in Tokyo. But all will soon be revealed!"

So there you have it. Does this mean that Kojima is already planning something? And what will be revealed? Is it a new game, some secret relating to Metal Gear Solid V? It's a long shot, but let's see if this comment actually translates into something concrete.