This is a tough situation for the company to be in. They need to find a perhaps crazy way to turn the momentum of the console around, and releasing the same kind of games they've been known to make for the last 20 years doesn't seem to be it at this point. Mario Kart will really be the litmus test of that statement, though.
But abandoning the WiiU or putting development support at minimal is the *worst* decision to make in this scenario. Especially the minimal support. If they let WiiU die after a huge 2015 drought... I think that's endgame for a lot of people. They would lose fan support, which they will need when the next platform launches.
However, to consider the possibility, I can see them giving support to WiiU with some interesting titles throughout 2015, and launching something akin to the rumored Fusion system perhaps March 2016 after detailing it at E3 2015.
I predict 3DS will need a successor after holiday 2015. It probably can't carry 2016, nor should it have to. And if there is any truth to the Fusion, behind which I do think there is some logic in terms of maximizing development potential AND being unique, that would be the perfect time to launch it. Hence, it would take over from WiiU.
For their talk of a QoL platform... who knows.
I personally think this schedule would look good outwardly, but of course the real kicker is whether or not their developers can actually give the WiiU solid support through 2015 while preparing a compelling launch and first few months of software for the Fusion. I might be rushing them, making games for the WiiU and forward isn't quite the same as for GBA, and it's a bit hard to imagine the 3DS teams being ready to develop appropriate software on such a fusion device at all.
They probably shouldn't wait for the WiiU or 3DS to slowly die and go cold before releasing a new platform, is my main non-speculative point.
EDIT: But they also shouldn't toss WiiU away like a bad apple.