With a bit of common sense, you understand december is not possible, PS4 will without a doubt sell more in 2015 than in 2014, saying otherwise is really knowing nothing about the market.
2015 has much more big system seller than 2014, PS4 will have a much bigger year in Japan, and also a big exclusive system seller for the end of the year
Predictions for end of 2014 HW sales:
PS4: 17m XB1: 10m WiiU: 10m Vita: 10m