I really believe Ninty will make adjustments to their sales forecast after the holidays. I think their strategy right now, is to hope there is not enough PS4 and X1 during the holidays and people will buy the Wii U instead and catch lightning there
Well, in Japan at least the PS4 isn't coming out until February, meaning the Wii U's only competition is the PS3, and the only big PS3 title coming this holiday is GT6. The PS3 shifted about 309k units in Japan last holiday. The new Wii U bundles in Japan have caused a huge spike in sales, with about 40k sold the week ending Nov. 2, and with SM3DW coming out and no PS4 to compete against, I could definitely see the Wii U winning this holiday season in Japan and perhaps even edging out the PS3 for 2013 sales (it's about 200k behind right now, and if the PS3 adds 300k this holiday, the Wii U needs at least 500k to match the PS3 for the year).
As for America and Europe, it's a bit tougher to call. The 360 and PS3 are still doing fairly well in both regions, and the PS4 and XBO are coming out as well. The former two will likely have a lot of steam let out of them by the latter, though, but they should still post solid sales figures (maybe ~3 million each). With stiffer competition in these two regions, it'll be interesting to see how the price cuts, new bundles, somewhat improved roster of exclusives, and the arrival of SM3DW (which is looking like it'll have a fairly solid launch) will help the Wii U sell in the coming weeks. However, we should also keep in mind that the 360 and PS3 are older systems that are in decline and will likely post lower sales this holiday than last, and as for the PS4 and XBO, early adopters are often not a huge force. The Wii U still had a fairly solid debut of around 900k in America and (NPD says 885k, while VGC says 933k) and around 450k in Europe, but it still didn't become the top system. Even the PS3 and 360 only sold 688k and 607k in their debut holidays in America, failing to outsell the aging PS2 (the PS3 had a February debut in Europe but sold 622k that month according to VGC, while the 360 sold 443k in the region). So, it's possible that the PS4 and XBO won't suck too much life out of the Wii U, which could likely end up being the top-selling eighth-gen system this holiday.
Every home console has done at least as good if not better during its second holiday season than in its debut holiday season (globally, at least), and I expect the Wii U will be no different. Even the GameCube managed to sell over a million units in the U.S. for the Nov.+Dec. period in 2002, and it was competing against the PS2, which had a year's head start on it and had sold a staggering 4 million units here that same holiday season. Neither the 360 nor the Wii sold anywhere close to that much in America during their second holiday seasons. Also, the GC had to fight the Xbox for the remaining scraps. By being the first out of the gate this generation, the Wii U has much more room to breathe than the GC did, and because of that I think it can do well this holiday season. It sold 2.2 million in its debut holiday, and it's in a better position than it was last holiday in terms of price, games, etc. While it's had a lackluster 2013 so far, I still think 3 million units worldwide combined for November & December is a distinct possibility. That's about what the 360 did during the 2006 holiday season and about 500k less than what the PS3 did in holiday '07, so it's not totally unrealistic.