AT&T has not officially announced that it will give access to 17,000 Wi-Fi hotspots to iPhone users, but the descriptions of the iPhone plans have been updated with this information on their site.

AT&T recently struck a deal with Starbucks to provide hotspots at their coffee houses. The iPhone plans still have the same pricing starting at $59.99.
Why AT&T is not blowing into the big marketing horn about free Wi-Fi for the iPhone is not clear yet. I do not think they wait until the introduction of the 3G iPhone. It is possible that we will see an official announcement today.
More details on the AT&T iPhone site. Via MacRumors.