sourceIn an interview with Famitsu magazine in Japan (photographed on Kotaku), Miyamoto has said that Nintendo is working on a brand new Wii U game that isn't part of one of Nintendo's existing franchises.
"With Mario Kart 8 coming out in the Spring of next year, we'll have a good selection [of Wii U games] available, so I'm thinking isn't it about time we release a new franchise?" reads the quote. Famitsu's follow-up question - "A new franchise! Would that a be brand new title that you would be working on?" - garnered the following response: "I can't talk too much detail right now, but I will say that this new title has been keeping me busy lately."
This would be the first brand-new game IP to be released on Wii U by Nintendo except launch title Nintendo Land - and though Nintendo has always innovated within its established franchises, since the Gamecube days entirely new games outside those franchises have been a rarity at Nintendo. Something totally new would be very welcome.
Nintendo needs new game types badly, though I hope this is centered towards it's core gamers.