It's not a fact, but I wouldn't bet against it. Nintendo pulled the plug very soon on the gamecube (it was practically dead after 2004), and it could only achieve that number after the price was dropped to 99€/$ after just a year or so. Also, the gamecube already peaked by this time while the Wii U is up yoy. All this means the Wii U is starting to catch up, albeit very slowly yet. If no new console comes out next year (which I'm pretty sure it won't), the Wii U will catch up and pass the cube in 2017 or early 2018 (and I think only that year the successor of the Wii U will come, although it can already come in 2017)