So they were probably around 9.9 mill in the beginning with August...that leaves roughly 5 months -including holidays- to reach 8m, from which 2m was done in 2 months....my bet is PS4 will end up around 16.5-17m. They don't really have a heavy hitter for the holidays..
Destiny, GTAV, Call of Duty, Far Cry, PS4 popularity, Holidays, Black Friday. Both PS4 and Xb1 will sell just fine.