So it appears XB1 will be competitive with PS4 as long as it keeps getting good deals out. It is looking increasingly unlikely that the XB1 falls 7-10m behind the PS4. So as long as the PS4 manages to get to 40m from the US alone, the XB1 will have 30m.
Things might change with Scorpio/ Slims and Neo though.
This leads into Lifetime sales discussions of there being the possibility that the XB1 sells close to 360 or PS3 globally