I have an outstanding strong relationship with the manager of my local AT&T store. I do Android, iPhone, and other business with them very frequently. Usually upgrading to the latest Android as they are released as well as other phones.
So my only point is I get really good reliable communication and info direct from the store manager as they are the only ones that AT&T keeps updated
They purposely keep the reps in the dark, since they have loose lips, tend to makeup stories and wouldn't sell anything in stock since they'd give out just enough "guesses" to keep the customers waiting (not by choice but by ignorance on the part of the sales staff)
So... that said, after speaking with him about an hour ago, he intimates they will have about 60 to 80 phones per larger major metro AT&T corporate store. The others will get less.
Being a slave to Apple, they do not get restocked daily after the initial order as Apple does with their stores. That's why I pre-order from AT&T, it assures me I always get my iPhone on release day if not a day early.
So that's the latest I have as of an hour ago.