Well, there is some inconsistency here between VGC and Nintendo's reports. Someone from VGC care to comment?
I think that Nintendo reports "shipped" numbers, and VGC estimates "sold" numbers.
This is why in Q1 Nintendo shipped only 0.16 million Wii U! They had a glut of stock.
Q3 Ending Dec. 31, 2012: http://www.nintendo.co.jp/ir/pdf/2013/130130e.pdf
The worldwide sales of the “Wii U” hardware were 3.06 million units and those of the “Wii U” software were 11.69 million units.
Fiscal Ending Mar. 31, 2013: http://www.nintendo.co.jp/ir/pdf/2013/130424e.pdf
The worldwide sales of "Wii U" hardware and software were 3.45 million units and 1.03 million units respectively.
Q1 Ending Jul. 31, 2013: http://www.nintendo.co.jp/ir/pdf/2013/130731e.pdf
The worldwide sales of "Wii U" hardware and software were 0.16 million units and 1.03 million units respectively.
Q2 Ending Sep. 30, 2013: http://www.nintendo.co.jp/ir/pdf/2013/131030e.pdf
... but the global sales of the “Wii U” hardware and software reached only 0.46 million and 6.30 million units respectively.
Current sales reported by Nintendo: http://www.nintendo.co.jp/ir/en/sales/hard_soft/index.html
As of Sep. 30, 2013: 3.91 million units
But don't get too excited. VGC has 3.68 million through Sep 30 which is not that far behind Nintendo's report of 3.91 million shipped.