The PS Vita has sold more this year and is currently ahead lifetime. This is including Japan, the WiiU's strongest market, and in Europe. While the Vita may not get any other major releases the WiiU has gotten nearly all of Nintendo's biggest franchises except for Zelda. Not to mention the Vita can still use a price cut (along with the memory cards) and it should be on the market longer then 2016. What do you think? 

It's possible, I think.

I think Wii U can and eventually will surpass PS Vita, Pokémon and Zelda will arrive on Wii U only next Year, as well as Star Fox and XC coming by the end of this year, plus NX not beeing even revealed means that Nintendo will support Wii U at least until early 2017...

PS Vita outsold Wii U every year in Europe. PS Vita outsold Wii U every year in Japan. PS Vita outsold Wii U every year in rest of the world. PS Vita is bigger in Europe, Japan, rest of the world and Global than Wii U currently. USA is the only market where Wii U leads. And PS Vita is bigger than Wii U in 2015 by now. And PS Vita will have a longer life. PS Vita will be bigger than Wii U lifetime imo.

Depends on when the NX shows up.
Im leaning more towards, it wont outsell the PS vita.

WiiU normally outsells Vita during the holidays, and by a large margin, so I think it can outsell it lifetime, but the gap will be small. Maybe 2-3 million at most.

The Vita doesn't profit nearly as much as the Wii U from the holiday season. And while Vita is still up front in Japan, the sales are going down there as well and are now very close to those of the Wii U, which is trending up.

So yes, I believe Wii U will get past the Vita

maybe, if they ever drop the price.

Eventually...

Not likely, the vita still has a 2 million unit lead against the WII U and while I think the gap may close somewhat by the end of this year it's anyone's guess as to how next year will turn out ...

If the WII U is not anywhere close to beating the vita next year then it will most likely never outsell the vita ...