2 things, which I am sure have already been covered in this thread.
1 - Black Friday week looks like the Xbox 360 will erase a good 500k or more from the lead in just that one week by itself. Makes it a lot more possible then for the remaining weeks to make up the deficit.
2 - We don't know for sure, or at least I have not seen it specified anywhere, whether MS meant the calendar year or their fiscal year. If they have until next June when their fiscal year ends, I am sure they will accomplish this feat with ease as they are in prime position for major price cutting ventures (Have been for over a year now, it's amazing they haven't cut the price in 3 years. They have to be making gargantuan profit margins on all SKUs).