Wii U by now should be 5.3 to 5.5 million units...
In January it should reach 5.7 while in best case scenario 5.85, Wii U will break 6 million in february and should hit 6.75 somewhere in March.
I estimate that Wii U by November will break 10 million and by end of 2014 will break 12.5 million...