I think Nintendo's fate rests primarily in the hands of Sony's PS4. If the muliplat games continue to look better on the PS4 as well as the continuous value in their own exclusives and hardware (Project Morpheus), then less people will want to pick up the XBOX One. Nintendo does not have 3rd party support, so it will have to show continued value with their first party exclusives. I feel that Nintendo needs to continue to bring the Zelda, Mario, Donkey Kong, etc. games to the market. BUT, at the same time, they need to bring new characters/experiences to the gaming industry to recapture the casual gamers that we all saw with the Wii.
In my honest opinion, XBOX One will more than likely take second place (even though I voted for the Wii U). The reason that XBOX One will take second place is because I feel that they hold their own fate. It is up to them to deliver those 1st party exclusives that gamers are searching to play. The console will sell despite having inferior graphics (Destiny for example), which are games that Nintendo fans will not be able to play. I feel that this steady stream of multiplats for the XBOX One will be enough to stay relatively close to Nintendo. The huge issue for XBOX is to catch up to Nintendo's one year head start. Also, it isn't a good sign that they have to catch up to Nintendo in sales when they are currently selling less.
Having Halo 5 be the sole reason as to why the XBOX One will catch up to Nintendo is wishful thinking. The main reason is because this game will release one year from now. This works completely in Nintendo's favor because that's more consumers buying a PS4 and not an XBOX One over a YEARS time at the beginning of the genration. One year is hardly a long time, but when the PS4 is selling this fast without their main lineup, one could only imagine how strong the PS4 adoption will be. As I said before, XBOX needs that wow factor to get people to buy an XBOX One to catch up to the Wii U. I just don't see them doing that (at this point in time), but I feel they will show more in the future (that would have to be sometime in 2016-2017, since they showed up until 2015).
My reasoning is the most recent XBOX One announcement, Gamescom 2014. When I watched their conference, I cannot be the only one to see Microsoft's E3 conference all over again with Tomb Raider thrown in there. I feel Gamescom was Microsoft's chance to show the gaming industry what they have been working on since E3. Since they didn't show any new Blockbuster exclusives at Gamescom, one can assume that Microsoft has shown all of their cards. As we all know, a timed exclusive will not propel the XBOX One sales as say Titanfall or Quantum Break. So until I see more must have exclusives, then I think the Wii U will take second place this generation. Releasing another Halo, Forza, or Gears WILL NOT help them in the long run. It will surely boosts sales, but it wont have the same impact as a continuous barrage of new IPs that they most certainly need.