Probably down a little bit.
N3DS will help slow down the decline but it won't stop it. It sold roughly 3 million in each major region, this year more like 2.5 million in each with a few 100k in others, 7.5-8 million worldwide is my guess.
As for Wii U, it could go either way. A price cut+more consistant release schedule could see sales increase or just prevent a decline, overall sales will be similar to 2014, 3.5 million give or take a few 100k.
Combined I think they will sell around 11-12 million.
When the herd loses its way, the shepard must kill the bull that leads them astray.