The PS4 will reach 50 million by September 2016. It will do it easily. Never in doubt. I told you so.
PS4 with its exclusive games and Xmas sales boost and boosts from big multi-platform titles like Fifa, Madden, NFL, NHL, Battlefield, Call of Duty, etc will do it easy.
2016 will be PS4 third year and possibly a 25+ million sales year. 2015 I expect PS4 to sell 20 million for the year to back up its 18 million sold from launch to end of 2014.