I'm guessing by the end of August.

But that's assuming a summer release of Smash Bros and a consistent software release schedule. Until I see a Nintendo Direct I'm not making firm predictions.

when will wii u hit 10 million?

Answer: Not this year unless they do something drastically (like releasing 3D Pokemon MMORPG).

Probably over the holidays

Hopefully just before the run up to christmas, so October 2014

it has to be(I think) this year around the holiday push,but yeah,its a friggin snails pace neck and neck with the vita most weeks

I'd like to think it should pass 10m this year, maybe even before the holiday season if Nintendo ups its efforts with advertising and game releases

If Wii U sales are 10 million LTD sometime in 2014, does it mean it will sell twice as much than 2013? If so, I think we won't see 10 million until 2015 unless Nintendo begins to aggressively advertise the system and releases a new and innovative game that makes use of the Game Pad that is hard to imagine but also fun to play.

Edit: I did some math

Wii U sales in 2013 LTD is around 5.479 million according to VGchartz numbers in 2012 and 2013

So Wii U needs haves 4.521 million to reach 10. Wii U sales in 2013 according to VGchartz are 3.232 million. Selling 4.521 million in 2014 means a 39.9% increase of sales in 2013. That is much better than needing to sell 50% more than 2013, but it's still a pretty big number.

december 2014

With the bunch of great franchises coming it is going to reach before the end of this year Nov or Dec

I believe it will do it in the beggining of 2015. Best case scenario are 2014 hollydays.