According to sources close to Digital Foundry, Nintendo has been in talks with third parties about their successor to Wii U. This has been going on for 18 months with Nintendo accepting pitches on the hardware:
"Around 18 months ago, during an informal chat with an extremely well-placed individual in the hardware manufacturing business, an interesting nugget of information dropped into the conversation - Nintendo was already accepting pitches from third parties on the hardware make-up of its successor for Wii U. Two names were mentioned: AMD and Imagination Technologies, creators of the PowerVR mobile graphics tech."
It is, of course, a speculative piece and all console manufacturers are working on future hardware at all times. But if Digital Foundry is right, it might indicate that Nintendo has reached a little further than most people might have suspected.