I'm not sure Wii U will ever pass Vita.

As for the X1..  well, if things keep going the way they are going right now..  then I would say Q1 or Q2 of 2015.  But I lot of things could change and Nintendo might pull something.

Wii U won't pass Vita, Xbox One will pass them both.

Xbox One will pass both Vita & Wii U. Wii U "may" pass Vita at some point, but I don't honestly know at this point whether Wii U can stay ahead in the long run. Wii U is selling at unprecedented levels of horrible right now.. its hard to believe a major comeback is ahead, but weirder things have happened.

Really good question. Japan is keeping Vita alive, the only potential system mover in the west, afaik, is going to be Borderlands 2 and from the footage I've seen, it only looks okay.

MK8 and Smash will do great for WiiU but I wonder if they will be enough to get the WiiU ahead of the Vita this year. IMO the fall lineup for WiiU doesn't feel like they will move many consoles.

I can't really speak to the fall lineup for the XB1 since the games supposedly coming out then, I've seen very little in the way of gameplay or story.

I'll guess that WiiU will catch Vita before XB1 catches WiiU. They could very well happen around the same time. WiiU has to sell 2mill on top of w/e Vita sells which means XB1 has to do 4mill on top of that.

Anyway, E3 is definitely going to be huge in deciding which will win this particular race. I'm hoping for great software for all the new consoles and handhelds.

Edit: I'll add that if WiiU does pass Vita, it probably won't hold that lead for long. Vita will likely get support longer than the WiiU. Look at the PSP.

Vita isn't doing that horrible either...It was only 18K behind X1 this week. Honestly, they just need to get more support in NA. If they do that, I can see it selling on par with the X1, cause right now Japan is a monster for Vita.

X1 will win out of the 3, WiiU will be last and Vita will keep warm in the middle

Well, the Wii U has 2 heavy hitters this year that we know of with Smash/MK. X1 only has Halo, but it also has a bunch of medium games like Quantum Break, Sunset Overdrive, and Fable Legends. There are also supposedly a few unannounced exclusives coming in 2014 IIRC. That plus good third party support should easily allow the X1 to outpace the Wii U, but whether it passes it before the end of 2014 is stil debatable. Vita is just getting a ton of Japanese support, and has had a higher baseline than the Wii U so far this year because of it. The Wii U has to sell 2m more than the Vita this year to outsell it, which is possible but probably not very likely. Even if Western support and numbers don't improve, the vita is doing well enough in Japan that MK and smash probably won't be enough to put the Wii U ahead.

Wii u will never catch Vita and Xbox one will surpass both of them.

I'm going to go out on a limb here and say that XO might stay in last place. Xbox had Halo and Halo 2 and that didn't manage to propel it past a cheaper system with more games. XO already had THE big hype exclusive shooter grace the console for the year and it had a minimal impact on it's trajectory. There isn't another until next fall or winter. I think there is a very real chance for an XO stall out in the same way we've seen with most other 8th gen consoles.

The AAA industry model is really working against it. With less and less titles costing more and more developers wont support the XO exclusively they way they have in the past with the 360. So it's less and less likely it can differentiate itself from the PS4 library. 3rd parties are probably all on board PS4 after Titanfall. MS has never had as much 1st party presence as Sony so I don't see them being able to make up the difference internally.

I can't see them cutting the price. The moment they start subsidizing it shareholders are gonna complain and we don't know if the new head is going to be nearly so generous with that warchest. I would like to believe it will do substantially better but the variables just don't seem to add up in it's favor.

Depending on how far apart Smash and MK are they wont be enough to maintain momentum for it to pass Vita.  If only because I don't see any titles outside of them that will really help in that effort. If only because it's so cheap to develop for and seems to have more active software purchasers in Japan than PS3 or PS4 Vita will continue getting more Japanese support. If Sony can ever get to 15,000 yen $149 We might even see the EU respond better to it as well.  

Xbox One will surpass both sometime in 2015.. Vita will stay ahead of the Wii U, and the Wii U will be last.

Xbox One really isn't doing that bad sales wise, and I feel that they will have a respectable E3. Vita is being supported by Japan, and has 2 million sales lead on the U... And nothing has really helped the Wii U...