Yeah this is sure going to be a better year; however this is probably the last year the system sells over 2.5 million worldwide. I kind of don't really see 4 million happening though. For the first 4 months of the year, this system will probably be either flat or down in some territories. The system's shipments in Europe will probably not match last year's as more and more retailers start dropping the system. There is also the PS4/One/cheaper 3DS/cheaper PS3/360 competiton coming.
They fiscal year starts in April, but yeah, I'd be really surprised if it hits 4 million shipped. However, we're talking numbers that are so low that I want to give it at least a little bit of headroom if they do something really aggressive like bundling in Smash and Mario Kart for free or whatever.
That said, I see the Wii U's major challenges this year as follows:
1.) The PS4 and Xbox One had a really solid start, and they have a lot of games announced for them, so confidence is high both from a publisher and consumer perspective.
2.) So far, leaks suggest an Xbox One price drop to $400 this year, pushing it into the more affordable range.
3.) By Fall and Q1 2015 (still in the fiscal year) we will start seeing more next-gen only games coming out. Some publishers have even switched cross-gen projects to next-gen. For example, Evolve spent most of its life as a current-gen/cross-gen game, but Take-Two is releasing it as a next-gen only title. Since current-gen sales are falling apart and a ton of PS4/XB1s sold up front, the number of publishers willing to do is likely increasing.
4.) The last of the Wii U's third party support seems to be drying up. We're at the phase where we're actively canceling DLC we already sold people on the system, and their three biggest partners (Warner, Ubisoft, Activision) all have major titles announced without Wii U SKUs.
5.) We're going to get new entrants into the console race this year, and some may be notably more on target with Nintendo's historical audience. For example, Amazon's box is already being carted around to publishers and given that it was supposed to launch this Fall, it's presumably coming out either Spring 2014 or Fall 2014. Google is also rumored by the WSJ to be doing the same thing, but unlike Amazon, they don't have a bunch of first party studios.
6.) With the advent of things like smart devices and major f2p games, judging by how sales have went, it appears many consumers who would have liked Nintendo's lower cost and/or pick-up-and-play approach now have a lot to do and can easily satisfy their gaming needs without them. I see that as a structural change and basically view them as audiences that Nintendo is unlikely to ever get back.