I do believe it'll get a successor in late 2016 but I don't think it will be discontinued before 2017. If they discontinued it in 2015, they would also need a replacement; at this point, that would likely become a stressed and forced half-hearted effort with little thought and planning behind it (essentially another Wii U) and it would make zero sense to go that route one more time. And their new business plans and fusion project is very likely not nearly far enough along to realistically be released and marketed already next year.
Nope, I say successor in late 2016 and discontinued in mid-late 2017, that's my guess anyway.
As for MK and Smash; I think they will sell below expectation but the biggest hit to take is that they will likely fail to sell enough hardware to really change things up on the charts beyond a few weeks.
Commercial flops though? No way, even if they do "poorly" compared to the expectations of the franchises, that will still mean several million sales.
Smash could suffer a bit more though, with the decision to launch it on 3DS months before the Wii U.
9 million by the end of 2014 is not as straighforward to dismiss as many could think, personally I had higher expectations, as can be seen in my sig but thus far it has performed quite a bit worse than I thought it would. I still believe the Wii U will have a good Q4 with another price cut, Smash and a sizeable marketing campaign and the inevitable new bundles (MK + Smash bundle would be a killer combo) but it seems that the three quarters leading up to that might be tough, and people are putting way too much stock in MK either doing the job all on its own or software that will end up as niche titles making any impact in the long run (the likes of Bayonetta 2). It looks like it will miss 10 million for sure, possibly by some margin, but if it falls below 9 million, I'll be quite surprised, that will require the Wii U to remain more or less flat yoy, which seems highly unlikely to me.