I think a pretty big factor to add to the list, and one that really hadn't been on anyone's radar prior to September, was the near universal critical praise and renewed gamer interest in Destiny with the release of The Taken King expansion. Destiny is experiencing a rebirth, of sorts, with many former players who'd lost interest now jumping back in with TTK. Their renewed interest and the mediahype translated into a lot of new users picking up the PS4 Taken King bundle (see Amazon rankings for the past 5-6 weeks for proof)
IMHO, Destiny: The Taken King is the one unexpected wild card that really pushed PS4 sales in September, and its momentum is continuing into October. Will it be a factor in standing up to Halo 5? Maybe not, but here it is Oct 3rd and that Destiny bundle is still in the 'teens on the Amazon charts.









