The Apple representative that reached out to AllThingsD is saying that in some stores, the iPhone 5s has sold out or they are currently left with a limited supply of certain models.
Included in that statement is definitely the gold iPhone 5s, which has a shipping date of October now listed online. CNet notes that the gold model went from a ship date of 1-2 days to 7-10 days in 10 minutes and then slipped to its current spot in less than half an hour. All storage space variations of the gold iPhone 5s have a ship date of October.
In other countries, the gold iPhone 5s is experiencing the same level of popularity. In France, the UK and Germany, the ship time at the online store was pushed back to October in a matter of hours.
The other models, silver and grey, had their ship times pushed back to a 7-10 day waiting period for those models to ship from the online store. The iPhone 5c, which is not enjoying quite the same level of popularity, is still available online in for shipping within 1-3 days.
Apple won't release sale numbers, generally, until after the first week of sale so we won’t have the specifics on just how high the demand is for the new phone. Apple experienced a lot of criticism for shortages during the release of the iPhone 5, so we’d have to assume they would have been better prepared this time around. Based on that fact, if they’re calling demand “incredible,” these numbers might be staggering.