Keiji Inafune somewhat unintentionally let slip that he's working on a PlayStation Vita game during his "The Future of Japanese Games" talk. After speaking of work on his upcoming 3DS title, King of Pirates, as well as his company's work in social gaming, he mentioned that he's challenging himself once more with the Vita.
That's the direct approach to discussing the future of Japanese games, right? Just tell people about a Japanese game that's coming out in the future.
Inafune didn't offer specifics on the game, nor did he say which of his two companies (Intercept or Comcept) is responsible for the project. In fact, shortly after noting the existence of the project, he asked everyone to forget that he said it, alongside a big smile (not dissimilar from his visage above).