I believe this trend will remain remarkably consistent for the entire gen. Even with Titanfall, the X1 can't step up to the pace of the PS4. And MS has very little to reverse the trend. Halo? Gears? Since these franchises are in new hands, it is doubtful they can attain same prestige of their predecessors. There's some good IPs in MS's portfolio, but very few true system sellers.
So assuming X1 + PS4 will equal 360 + PS3, since they represent the core gamer market(plus the semi-casual gamers that follow what's popular), that puts PS4's lifetime sales over 110 million and the X1 right around 50 million. Not bad for the X1. It'll get 3rd party support, but not as much as the PS4 in the years to come.
I predict NX launches in 2017 - not 2016







