UPDATE: Here's Iwata's quote on the NX, translated officially by Nintendo:
As proof that Nintendo maintains strong enthusiasm for the dedicated game system business, let me confirm that Nintendo is currently developing a dedicated game platform with a brand-new concept under the development codename "NX". It is too early to elaborate on the details of this project, but we hope to share more information with you next year.
Also, Iwata said Nintendo's new membership service would play a key role in NX.
Nintendo, together with DeNA, will jointly develop a new membership service which encompasses the existing Nintendo 3DS and Wii U systems, the new hardware system with a brand-new concept, NX, and smart devices and PCs, and Nintendo will be the primary party to operate this new membership service.
Unlike the Club Nintendo membership service that Nintendo has been operating, the new membership service will include multiple devices and create a connection between Nintendo and each individual consumer regardless of the device the consumer uses. This membership will form one of the core elements of the new Nintendo platform that I just mentioned.
ORIGINAL STORY: During a press conference in Japan Nintendo boss Satoru Iwata mentioned new hardware, codenamed NX.
The press conference was held to announce a partnership between Nintendo and Japanese mobile game specialist DeNA to create mobile games based on Nintendo's intellectual property.
Nintendo also plans to create a new membership service, with DeNA, that will work across all Nintendo hardware, mobile devices and PC.
It was while announcing this new membership service that Iwata mentioned the new NX hardware.
Here's the direct quote from Iwata, which we captured and published in video form below.
"Nintendo, together with DeNA, will jointly develop a new membership service, which encompasses the existing Nintendo 3DS, Wii U, the new hardware with a brand new concept NX, smart devices and PCs."
At this stage it's hard to tell what the NX is, exactly, but in an image published on Nintendo's official website, it's described as a "dedicated game system", which suggests a home console of some kind. We're told more information will be revealed next year.