Apple's yearly developer conference should see iOS 8, OS X 10.10, and likely some hardware.
Apple Preparing to Release Updated AirPort Express Base Station
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."Similar references to updated Time Capsule and AirPort Extreme models were discovered in the public release of AirPort Utility 5.5.3 back in June, with the new models debuting a week later.
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"
That update brought increased storage capacities for Time Capsule models, as well as improved range and performance. It is unclear exactly what changes Apple has in store for the AirPort Express, but similar wireless performance improvements may be the focus of the update.