I'm using data from Nintendo in the data from the past and my thoughts for future numbers... I will also include GameCube numbers just because its slightly comparable... and I think Wii U will last to 2018.... but possibly 2019.. either way it will outsell GameCube

2012- 3.06m

2013- 5.86m

2014- 10.41m  (I believe in smash bros and hoiday boost)

2015- 17.03m (I believe this will be Wii U's peak year)

2016- 20.78m ( I think Wii U will have okay legs for Nintendo consoles)

2017- 23.99m (when it will pass up GameCube if it does)

2018- 25.01m (becomes almost dead)

2019?- 25.48m (Wii U's last year where its now dead)

Now GameCube numbers

2001- around 3m

2002- around 9m

2003- 13.94m

2004- 18.03m

2005- 20.61m

2006- 21.52m

2007- 21.74m

PREDICT Wii U numbers

2014 - 9.6 million(beating Nintendo expectations)

2015 - 14.3 million

2016 - 17.2 million

2017 - 18.9 million(successor launched)

2018 - 19.5 million

2019 - 19.8 million

lol maybe... I have more faith in Wii U than I should. Even though I have mine at 25m I think it most likely will be N64 levels and maybe more. But I don't want to many Wii U haters attacking me on how its impossible

2012- 3.06m

2013- 5.86m

2014-9.5m

2015- around 14m

2016-around 19m

2017- around 23m

2018- around 25m

2019- around 25.5m

I think the successor will already arrive 2015 or 2016.

2012- 3.06m

2013- 5.86m

2014- 10.00m (smash bros and holiday boost)

2015- 15.00m (Wii U's peak year with Zelda and Xenoblade and some unannounced AAA games)

2016- 18.00m (Nintendo Fusion is released)

2017- 20.00m (becomes almost dead)

2018- 21.00m (Wii U's last year where its now dead)

2019?- 21.50m (Wii U is dead)

2012 - 3.06m
2013 - 5.86m
2014 - 9.40m
2015 - 21.70m Due to Zelda, Xenoblade, Yoshi, etc.
2016 - 47.84m More AAA titles + Tons of Indies and JRPGs
2017 - 56.55m
2018 - 63.73m Nintendo Fusion is released
2019 - 70.02m WiiU stops being supported

2012 - 3.06m

2013 - 5.86m

2014 - 11.00m

2015 - 19.00m

2016 - 27.00m

2017 - 36.00m

2018 - 42.00m

LT - 45.00m

According to Nintendo (VGChartz):
2014: 11,000,000 (10,500,000)
2015; 20,000,000 (19,500,000)
2016: 28,000,000 (27,500,000)
2017: 34,000,000 (33,500,000)
2018: 38,000,000 (37,500,000)
2018: Coming new Nintendo console

LT: more of 40,000,000 (little less of 40,000,000)

9 million at then end of 2014. Dont know what the future holds. But if the case with Phillips goes badly then Wii U might stop being sold.

2014: 10.5m
2015: 18m (peak year)
2016: 23m
2017: 28m (successor released holidays)
2018: 30m
2019: 31.5m
2020: 32m (discontinued)