I have historical records of NPD going back to Oct 2000 (PS2 launch). I saw some people on another board predicting 360 would sell 1-2 million in the NPD that GTA comes out. Of course I knew that was ludicrous, but it prompted me to take a look, what where the highest non November/December months ever? Forget 2 million, had a console (not handheld!) ever even done 600k in a regular (regular will mean non Nov/Dec from here on) month?
The answer was no. The all time champ in that dept was the PS2 in March 2001, at just 546k. In more recent times, the Xbox 360 got surprisingly close to this number in September 2007 when Halo 3 released, clocking 527k systems sold. The PS2 actually beat 500k many times, I didn't count but I would guess it sold over 500k in easily a half dozen regular months, but never more than 546k. The Wii also pulled off two barely over 500k+ regular months in late 2007.
Anyways, I think the 360 could beat this 546k number in GTA month (April or May?) PROVIDED the recent euro price cut (which would provide a 199/269/369 lineup) finds it's way to our shores prior. Not only that but I think it would also need the rumor of the 60GB hard drive going in the premium to also be true and accomplished by then, and of course good supply etc. At that point a 269 Premium selling with a 60 GB hd, and GTA out, might have a chance I think, but it's still unlikely.
One factor to consider is the five week NPD months. It will be easiest to break this record in a 5 week month. Which are March, June, September in regular months. So this wont help GTA out.
As far as PS3, I see no chance anytime soon, the price is too high, but I suppose MGS4 in June might be the closest near term opportunity.
Wii could probably pull off the record almost any month, but it never has the supply necessary. But considering it had 500k+ regular months in late 07, it seems easily possible that with the right supply it could easily challenge the record in months such as Sep or Oct 08, it will just be a matter of chance.