I think Nintendo will ride this out for six years so 2018 I think we will see an announcement and release a la the PS4/Xbone. Now that the Wii U seems to have reached a comfortable level of profitability (we'll have to wait and see to be sure but it seems to be getting there), I think Nintendo will want to recoup losses from early in the gen. Also, while having no 3rd party support burdens the company it also let's them flex their muscles as a developer; I think they will follow up what they did at this years E3 with more gamer-focused press events to build the company's reputation and improve awareness of the depth of their IP. I think we will see more new IP as well as more promotion of their core-gamer-orriented IP (like Xenoblade, Metroid, etc) to achieve this end. I also expect to see a number of IP get representation on Wii U (I am banking on F-Zero's return personally). Also, 2018 would give Nintendo a lot of room to develop a stellar launch title like a Zelda or full 3D Mario supported by one of their younger IP that is more core orriented like Xenoblade.
Even if the max they can achieve sales wise is between GC and Xbox original sales, if they can come out with a much stronger image, it will be to the benefit of their new console. Plus, waiting until 2018 guarantees they can easily blow past the PS4's power by a substantial margin and keep the starting price reasonable.







