According to http://www.vgchartz.com/forum/thread.php?id=41981&start=0 on average 4,009 copies of gears of war on average was preorderd at gamestops throughout the untited states.
According to http://www.gamestop.com/gs/help/About_Us.aspx there are 4,400 stores in the united states.
I know not all the store are the same so I will say around one million preorders at gamestop alone. so t would have to be 1 million + preorders.
And imagine if you add the preorders with European preorders. 
This game could get to 1.5-1.6 million preorders in all.
These are just my thoughts that I believe can come true.
Would like to hear your opinions on this....
This can get as big as Halo...








