Wii U successor 2017 or 2018?

[Burek]

I don't see a point of releasing a new console any time soon. Or, basically, any time at all.

The games already look good enough on WiiU, any progress in graphical fidelity will be minor (or barely visible to the majority of people interested in those games).

The new console will still not have 3rd party support - I believe developers and publishers are quite happy to have a duopoly and a healthy competition between Sony and MS, with an occasional added bonus of PC. I seriously doubt that they would start investing serious money into another version of the same game for marginal results (as I doubt that Nintendo machines will ever again be embraced by a wide variety of gamers).

Nintendo has painted itself into a corner, a corner populated by hardcore, lifelong Nintendo fans, and I doubt that they will ever be able to exit that corner and attract general population away from PS4/XOne.

So, I think they should stick to WiiU for a long time, and once they reach the limit, simply produce a "New WiiU" (like they are doing now with 3DS).