This is a prediciton I made back in January 2014 after we heard about Q4 2013 numbers.
It's been pretty on point so far. And just to clarify, I am talking about shipped numbers here. Hence the 3.9m for X1 in Q4 2013. For PS4 I took the 4.2m number and started with that as we don't have a shipped figure for the PS4.