You should go today to your local store and ask what they have available. If you're lucky, they'll tell you what they got exactly otherwise they'll probably give you a ballpark number. I get the feeling 6+ will be gone fast (like maybe 1-2 units), 6 you might not get the size/color you want but you'll get at least something.
Still back to my point, highly recommend you go down there and ask. All we can do is speculate for you here. I think back when I was with AT&T, for the iphone 5 I went at about 5am and was about 14th in line. I got the second to last silver 16gb and my friend behind me got the last black 16gb. Everyone else had to get different larger capacity models.