My prediction is Wii U in second at the end of 2014 (ahead of xbone). After that probably Xbone (will be ahead of Wii U) but who knows. Things can easily swing both ways.

Guys, let's be realistic here. There's no war between XBO and the WiiU, but the WiiU will certainly win. Let me explain you how...

I see loads of people saying the XBO will obviously win over the WiiU because they have better graphs and 3rd party support and so on, and the Nintendo guys saying that the WiiU will win 'cos it has much more cool games and so on, but the 2 key points are: (1) the real competition this generation is between XBO and PS4 (specs, audience, hype, marketing, same games and so on), and (2) PS4 will keep selling so much more and hurting XBO so much that the WiiU will eventually KEEP the second place until the end of the generation, as it targets a different audience than the former two and has a lot more meaningful exclusives.

It's so much true that the WiiU is still almost 2 MILLION consoles ahead of the XBO, even after Titanfall and Watchdogs and, not even counting this last week when it outsold the XBO by more than 3 times (or about 135,000 consoles more), XBO was selling, before MK8, about 20 thousand more hw units worldwide, what means that it would take about 2 years to reach the Wii U (1.8 MM difference / 20,000 units weekly = 90 weeks). And it if nothing happened but, as we just saw in a MK8 vs WatchDogs lauch week*, many things can still happen, and when they happen to help the WiiU it surfs alone in the Hype, but when it happens to help the XBO, it's eclypsed again by the PS4 (and I'm not happy to type it, as I personally prefer the XBO over the PS4).    *And this is not even a real comparison, as WatchDogs was around for the whole week, and MK8 for just the weekend!

Finally, having settled this in a very clear way, we can imagine that Nintendo will be left then forever to a  distant second place in the VG industry, but that's most probably not the case... Let's try to make a funny and hars exercise and try to figure out what will most probably happen in the long run, in the comings of the next gen:

MS, who's facing each time more and more competition of Apple in their core business, computers, and pressure from the shareholders about the XBox division, will most probably either leave the VG industry (unlikely), either do a significant move (as they're already signalizing) to further integrate their computer and gaming products, including a very simple thing to do and which has not very much been done yet: playing PC games on your TV using a more XBox like operating system in your computer and direct wi-fi connection for the tv screen and controls. That's a new horizon for gaming, but the doom of the home consoles industry, in a tsunami which will not only wash XBox out, but the PS4 or PS5 (if it's ever released) as well.

The only possible survivor(s) in this scenario will be the companys which are not selling videogame consoles, as they will vanish away, but the companies selling playing toys and collective gaming machines, which allow for playing designs not allowed by the computers. And guess who's better designed for doing that, almost exactly as happened in 1983 after the 1st big videogame crash? 

Well, time to play MK8, buy a digital version of WatchDogs for my PC and start to dream with Zelda, SSBB, X and so on! (and to buy Nintendo stocks too! lol )

How like man? It's still not second place and, seing by their sales trends and incoming games and so on, XBO will have a really hard time even reaching the WiiU, let alone beat it!

I like XBox and would buy it instead of a PS4, but it is very unlikelly that it will be a leading console this generation. My predictions by the end of this year are WiiU 10,5 MM and XBO 8,7 MM, at the most! (let's talk back next January!;)

XB1 isn't going to be the type of console pulling 2m holidays, I know it's a case of waiting but XB1 will outship WiiU by the end of September.

Not even Nintendo expect 10.5m by the end of this year, and judging by the poor boost MK has given (it needed to be far bigger to achieve their FY goals) it's not going to surpass their expectations of about 9.6m sell through year end.

Honestly, I know you're not going to agree with me or think I'm just being unreasonable but I don't think you actually know any of this stuff.  I do think it's a possible interpretation, but the simple fact is that if things were as easy to see as you make it seem like, making successful new products would be extremely easy to do.  Saying the problem is with the system itself for the Wii U is based off of your speculations on the sales trends, internet comments, your personal bias, and the lack of substantial boosts with some of the bigger titles.  Some of these are strong, but none of them are conclusive like you're assuming it is.  

Another thing is that it doesn't need to go from 90m to 20m as your comment stated it would be "tens of millions" ahead of the Wii U.  I'm arguing against the statement that you know that the Wii U will be 20-30m LTD and the XBO will be 50-60m LTD.  It's the most logical prediction, but it's a prediction.  Saying it will vs saying that it might (with a strong emphasis on how likely it is) are two very different things.  A lot of your predictions do make sense, but the problem is as I said before.  

I argue on the camp that there are quite a few other factors here and while things seem to be locked into place, there are still things that could happen during the course of its life time that could make a difference.  

I do think that, as long as XBO does indeed recover, the Wii U has almost no chance of selling more than the XBO.  But, if the Wii U does pick up momentum with some of the new changes Nintendo makes, I don't think the gap will have to be 30m+.  It could be as low as 10m.  Is this what I actually expect?  No.  As things stand now, the Wii U will be last and the XBO will likely pull ahead as it has a stronger foundation.  But that doesn't mean you're right.

If PS3 could hit 80m then I think the PS4 can as well. 

Nope. WiiU can't recover, casuals are not interested for multiple reasons, core for obvious reasons. XBO has a very sizeable userbase to appeal too. It really is that simple, doesn't need extensive analysis.

I will be right in time

How many examples in history do you guys need before you realize MS can't spend their way to domination/success?  Zune?  Bing?  Windows Vista/8?  Tablets/phones?  Heck, we had an example just a few months ago; Titanfall.  MS threw money at EA for exclusivity on MS platforms, with the overwhelming focus of advertising on the One.  Paid for tons of advertising.  You couldn't go two commercial breaks without seeing an ad for it.  Then, before its release, MS subsidized a $50 price cut at every major retailer PLUS packaging the game for free.  What does their wallet have to show for it?  Obviously, nothing to brag about, cause they still haven't released how many copies sold on the One.  AND they were still comfortably beaten by the PS4, WW and in the US.  If the consumers think the One is a 20M-30M console, that's exactly where it will end up.

And if you think MS is going to spend money like it did during the OG XB and 360 days, think again.  They have big investors starting slight rumbles with talk of a spin-off or selling of the Xbox brand, since it still hasn't been profitable, overall, and they probably see the way this gen is playing out.  They don't want MS throwing money down a hole, just to come in a distant 2nd.  And we have even had Gates, himself, say he would be fine with a spin-off of the Xbox brand.  While they may never do it, they are at least seriously discussing it as an option.  And after the gap has grown as large as it will this year (anywhere from  ~6M to 10M, depending on how the holidays/game announcements play out), companies are going to be demanding more money from MS if they want the game exclusive, true or timed.

@ OP

If you had asked me earlier this year, I would have said it would be the One in 2nd, definitely.  Now, I'm not so sure.  The Wii just added 135K to the lead it has on the One (if this weeks numbers are true.)  The One will have to outsell the Wii U by 10K (about what it did last week) for over 3 months to make that up.  If the One price cut does little to no effect, and if Nintendo plays their cards just right ($249 price, plus another system seller or two, for the holidays), I can definitely see them securing 2nd.  Mainly, the people who are are interested in the One will also be interested in the PS4, and will discover that it is more powerful and has better multiplats with very little research.  The Wii U, however, interests people for reasons other than next gen graphics and the best 3rd party support, mainly Nintendo franchises and family friendly games.

Just for now but the xbox will claim its throne in the us again. It will sell more than the wii u and ps4.

http://www.theverge.com/2014/5/27/5756062/microsofts-nadella-xbox-isnt-going-anywhere