2013: 4.2M
2014: 14.3M
2015: 17.4M
2016: 17.5M
2017: 20.2M
2018: ~21M ?
This prediction assumes a permanent $199 price cut this year, if not, it won't reach it. If it does, 2018 will be peak year.
My previous yearly predictions which I've been doing since the start of this gen:
Prediction: PS4 will sell 20,000,000 by Dec 31. 2014
http://gamrconnect.vgchartz.com/thread.php?id=176130&page=1
Prediction: PS4 will sell 37,000,000 by Dec 31. 2015
http://gamrconnect.vgchartz.com/thread.php?id=196338&page=1
Prediction: PS4 will sell 55,000,000 by Dec 31. 2016
http://gamrconnect.vgchartz.com/thread.php?id=212195&page=1
Prediction: PS4 to sell 72,000,000 by end of 2017
http://gamrconnect.vgchartz.com/thread.php?id=224553&page=1