Very interesting, I wasn't aware 360 was closing the gap, much less by 2.6 million in the last year.
Should be a fascinating race to watch from this point on; the platform totals page has Xbox 360 at 49 million in NA, not sure how much of that is in the US though.
EDIT: Nvm just read the article; "The Xbox 360 sold 45.14 million units lifetime in the US. The PlayStation 4 needs to sell another 14.79 million units to surpass the Xbox 360 in the US."
This holiday season will be a bloodbath
360 did 3.4 million in Nov+Dec 2011 NPD while PS4 will probably be half of that (~2.3m last year).
When the herd loses its way, the shepard must kill the bull that leads them astray.