It didn't take long (just a couple of hours) for the initial stock of iPhone 5s to sell out, as the Apple.com site slip their ship date from September 21st to September 28th in the wee hours of the morning. Throughout most of the day, U.S. carriers AT&T, Verizon, and Sprint still held the September 21st ship date, but as we close the work day, all three carriers have pushed back their shipping estimates.
AT&T is showing that they'll ship all models of the new iPhone in 14-21 days:
Verizon is saying they'll deliver by September 28th:
And Sprint is showing 2 week ship time for the 16GB, but the 32GB and 64GB remain on schedule. That's likely to change at any moment, however: