Nintendo CEO Satoru Iwata revealed last month that Nintendo is working on a new dedicated gaming platform codenamed NX. No specifics were given, and Iwata said he hoped to share more next year. In the meantime, a principal test engineer at Nintendo has updated his LinkedIn profile to indicate that Nintendo has multiple devices in the works.
Nintendo's Lu Yang marked under "Experience" that he has spent February 2014 until the present working on "Platform Tools for current (Wii U) and next generation (unannounced) consoles." Nintendo typically starts brainstorming for the next handheld and home consoles immediately after their current one is released, but the fact that they're creating platform tools for multiple consoles indicates they're a little further along.