I think that combined first month, sales will be about 5 million, possibly higher if the hype is that huge. By the end of the first year, expect sales to top 12 million combined.
First month:
Xbox 360: 3 million
PS3: 2 million
First year #'s:
360: 7 million
PS3: 5 million
This of course is all dependent on how sales after the release break down. If alot of former PS2 gamers buy the PS3, expect the first year numbers to be a dead heat between the 360 and PS3 and possibly the PS3 being "slightly" higher.
Initially with the 360's user base being much larger, it will sell more on that system, then you'll see the PS3 eat into the lead.
This is of course my "prediction" and is based on nothing more then my guesstimations.
My pokemon brings all the nerds to the yard. And they're like, "You wanna trade cards?" Damn right, I wanna trade cards. I'll trade this, but not my charizard.