Well they have 1.4m on shelves at end of 2014... so I guess they decreased this number to 1 million on shelves.
That means from Jan to Mar they sold 2.8m PS4s... almost 1 milliom per month.
Was about to edit my post^ I made a mistake i switched the 1.4mil (sold) with 2.4mil expectation!
Again my bad for the mix up. I wonder how psp is still selling? Vita TV might be discontinued this year however.