I agree there's no reason to drop the Wii U quickly. Nintendo need to take their time getting online and accounts working nicely (Smash and MK8 work pretty well but overall still not as good as Xbox 360's online experience). The fusion concept is cool but who knows with Nintendo. I think they should wait until after they establish a strong smart device presence and then use that to market the next console.
If the first mobile games start releasing this fall, I'd guess it take about a year for Nintendo to dominate the games market on iOS and Android. Then they can use the next two years to develop a strong launch lineup and build third party relationships. So I think they should release the next console by fall 2018. They have to market the console like crazy especially through their mobile games.
I want NIntendo to have a strong launch lineup for their next console and also support the Wii U for a long time still. Maybe this is all too much to ask of Nintendo, they don't get third party support to help take some pressure off of them. I feel bad for their employees actually, the next 5 years for them will probably be hell :(
