Based on past comments from Nintendo, and their thoughts that they'd like the handhelds and consoles to operate more closely together, there's absolutely no reason both a new HH and a new console could not launch together in 2016.
It might be the best way for one last go at the console market to work for them.
It could also be used to give the Wii U titles for about a year as well right? It'd also give an excuse for Japanese parties to release stuff on the Wii U (kind of like how they do with the Vita & PS3 and now Vita & PS4).
The current situation of the Wii U really isn't tenable.
They can't continually cash checks and lose loads of money to buy retail space, and at some point the retailers will want to put something else there anyway if things aren't selling.
The 3DS, while declining, at least is actually a notably physically smaller object and is selling better than its counterpart.
Although by next year, what's stopping the 3DS from selling Wii U like numbers as well in the West? The revision pretty much seems like the only thing apart from a bunch of the titles releasing in Japan now/soon (Bravely Second, Final Fantasy Explorers, MH4U, etc.)