Preview at WWDC likely in June, followed by September launch.
AT&T Officially Lists Wi-Fi Hotspot Access with iPhone Plans [Updated]
AT&T's iPhone website (under 'Plans' tab) has been updated to reveal that each iPhone plan now includes access to their "more than 17,000 Wi-Fi hotspots, including Starbucks all for use in the U.S."
It was first revealed last week that AT&T had quietly begun offering iPhone users access to their Wi-Fi hotspots for free (including Starbucks and Barnes & Noble). No official announcement had been made, however, and the service was abruptly turned off a few days later.
AT&T has remained quiet about this new offering, but it's clear they will be officially delivering this service shortly.
Update: AT&T has changed the text on their site to remove the Wi-fi reference. They delay may be due to the fact that AT&T Wi-fi has not yet been universally deployed at Starbucks.