The thinking all along was that there'd be an allocation of unreserved iPhone 4s in AT&T stores this Thursday for customers who didn't bother to (or couldn't) pre-order the phone ahead of time, but not so much. Turns out that the extra stock won't be arriving until June 29, at which point it'll be available on a first-come, first-serve basis...
http://www.engadget.com/2010/06/22/no-pre-order-atandt-wont-have-an-iphone-4-for-you-until-june-29/
http://www.engadget.com/2010/06/22/no-pre-order-atandt-wont-have-an-iphone-4-for-you-until-june-29/