Wall Street Journal, via Kotaku, has details on the next Nintendo console/handheld/maybe both?
The exact shape of the NX hardware isn’t yet clear. People familiar with the development plans said Nintendo would likely include both a console and at least one mobile unit that could either be used in conjunction with the console or taken on the road for separate use. They also said Nintendo would aim to put industry-leading chips in the NX devices, after criticism that the Wii U’s capabilities didn’t match those of competitors.
An addition later on explains these may be marketed and sold as difference device - this sounds like a Playstation + Vita, where you could also still buy them separate but they're more tightly connected. Games would work on both, though probably not the same.
The article says they're hoping to release by next year, but that seem optimistic if they don't know what it looks like yet.