updated 09:30 am EDT, Tue September 3, 2013
Unit could be refreshed at September 10th Apple event
A number of Apple Store and Best Buy outlets are out of the AirPort Express, inventory checks show. While Apple's online store and some of its physical locations have units ready, many shops are listing the Express as either "Unavailable for Pickup" or something that has to be shipped in. Affected Best Buy stores are simply out of the product.
The depletion suggests that Apple is planning to either refresh or discontinue the Express in the near future. More likely is a refresh, presumably adding support for 802.11ac, which is already built into the AirPort Extreme, Time Capsule, and MacBook Air, and should reach the rest of the Mac lineup by the end of the year. Apple could launch a new Express as soon as September 10th, the date of a widely-rumored press event. While the event should be focused on iPhones, Apple may choose to launch new Macs around the same time, and/or update some of its peripherals.