Yeah this is a no no for me. You could reasonably expect the PS4 by end of September to be around the 27 million mark. But that would still require the Xbox to sell less than 2 million from March - September (7 months!)
7 months is about 29 weeks or so, 2 million divided by 29 weeks is 69,000 per week. There is no way the Xbox will sell as little as that as an average from here until September. There will be numerous spikes to those sales as big games come out but I can't see the xbox dropping to the required number on any given week between now and then.
PREDICTIONS FOR END OF 2015: (Made Jan 1st 2015)
PS4 - 34M - XB1 - 21m - WII U -12M