To be honest XBOX has only increased its lead by 800,000 since Jan 09, which is basically a year and a half (i.e. Jan 09 8,500,000 - april 10 - 9,300,000).
The graph is also clearly stabilising, so you could be waiting a while to get to 10,000,000 ahead...
Nah, even after a price cut, slim ect ect the PS3 has done hardly any damage to the 360. When it's time for Microsoft to do something big with the Xbox (Like NXE and price cut in 2008) it sells massively in the states.
It's not really a contest who will sell more in NA this christmas, PS3 barely won it last year didn't win it last year, 360 will cake walk it this year. WW is a whole difference story, that's anyone's guess.