Although Apple's online store still reflects availability of "AirPort Express Base Station with 802.11n and AirTunes," authorized resellers like DataVision report that the same model (MB321LL/A) is discontinued, while Amazon estimates it will have new stock sometime in the next "2 to 5 weeks."
Additionally, a person familiar with the matter says Apple is wrapping up the release of AirPort Utility 5.6, makes reference to a second-generation 802.11n AirPort Express in its developer notes:
"Adds support for the AirPort Express 802.11n (2nd Generation) base station"
The current version of Airport Utility, 5.5.3, was released in June, resolving an issue that caused the tool to unexpectedly quit during setup.
The update would round out tune-ups across Apple's AirPort device family. In June, the company quietly updated both its Time Capsule and Airport Extreme base stations. Though no specific changes were detailed in product specifications, FCC filings revealed that the new devices had received a power boost of as much as 2.8 times the original signal.
Subsequent tests revealed dramatic performance and reliability improvements to the base stations, especially when accessed from more remote locations. A teardown of the AirPort Extreme also showed that Apple has switched from Marvell WLAN cards to the Broadcom BCM4331.
But, given that FCC filings for a new Airport Express have yet to turn up, it remains unknown whether the diminutive base station will also see a signal boost when it is updated.
Apple released the first generation of 802.11n-capable AirPort Express routers in March 2008, billing the device as the world's smallest 802.11n-based mobile base station.
As Apple has been hard at work prepping its iCloud service, rumors have swirled that the company may transition its AirPort base stations to use iOS, with some reports speculating that software updates could be delivered wireless via an AirPort router.