They're saying if they run out before you can get one on Friday, that they'll lead you to the computer to order one online so you can get it within three or four days. This makes sense because with the holiday next week the best you could hope for is a Thursday delivery.
It depends on how long you wait to order one. If I were someone that missed buying one in person, I would be ordering as quickly as possible. I could see online inventories running out eventually, but not on Friday night.
I agree...the lines will probably be sort of long, but there are so many AT&T stores and at least one Apple store...plus you can order online...too many options for someone who really wants one, not to get one