Nintendo has its usual recruit page for developers who want to join their Kyoto or Tokyo R&D facilities. But in addition, they recently added (1/19) an urgent recruitment listing for contract level designers for 3D action game in the Tokyo R&D office.
https://www.nintendo.co.jp/jobs/care...yaku.html#3dld
Is this regarding a secret 3D Mario or 3D action game for NX from the Tokyo production group? Definitely hinting at that.
Note: Tokyo Office is where Galaxy, 3D World, Captain Toad, NES Remix, Flipnote Studio, Nintendo 3DS Guide are developed. Most other franchises developed in Kyoto office.
Update: Yoshiaki Koizumi (EPD Tokyo) also retweeted the NCL hire listing on his personal twitter.