i see it like this

xb1 passes wiiu before this yr ends
xb1 passes vita early or mid next yr

vita vs wiiu to early to tell cant see WiiU passing it this yr or next

Well considering the Wii U only outsold Vita by only 20k units in all of 2013 (both had equally barren release schedules) and the fact that so far this year the Vita has outsold the Wii U every week but one tells you why people are thinking the way they are. Vita's found a niche in Japan to help sales, WiiU hasn't found a niche anywhere. Also Playstation consoles have a habit of staying on the market longer than Nintendo ones so that may play a factor.

And as far as Mario Kart and Smash are concerned, Super Mario 3D World was the first game that was supposed to raise the Wii U's baseline and so far it hasn't so who's to say Mario Kart and Smash will make a 2 million unit deficit disappear. I'm not saying it won't happen but at this point it's looking very unlikely.

For the vista, I think it will be last, the sales are so low in EU/US that it's really dying. I can't see Sony or any major 3rd focusing on it. But with a 2~4 millions lead, it will take years. It's just so hard for the wii U or xbox to sell 1 million console, it takes 4~10 months, and it takes a hell lot more to outsell for 1 million another console.

I think Xbox 1 will not pass the U (or very late). We are currently 2 weeks away from the massive launch of the exclusive Titanfall, with stockpile to sell, bargains, advantage in the US, and the xbox 1 only manages to sell 90K. So it's potential average sale outside the current multiple effects could be as low as 50K/week, and probably not higher than 65K. On the contrary the Wii U at its lowest with 40K sales is still waiting for MK8 and other strong legged sellers, so it could go up to 50~60K. Nintendo should slightly outsell for Christmas, making up some of the difference. A 20K difference means it would take 2 years for the Xbox 1 to pass the Wii U. a 10K difference takes 4 years. If both just outsell temporary for major launches, it will take forever.

based on the fact that its been outselling it by a good margin all year. And it usually outsells it out side of the holidays which is 9 months out the year. But you dont seem convinced so when DO you think Wii U will finally pass it?

What do you think wiiu will ?  wiiu will do what 2.5/3m in sales this year maybe.  It selling 15m lt is doubtfull.

The Wii U will easily pass the Vita this year( thanks to games like Mario Kart 8), but the Xbox One will most likely outsell both of them!