AT&T has been holding seminars for prospective Windows Phone 7 developers. During their Q&A, published here , they reassured the attendees that the iPhone carrier will in fact carry a handset at launch after all.
While this is not new information (Microsoft said as much at Mobile World Congress) that is now a long time ago, and we have all seen how long it took for good Android handsets to come to the GSM carrier.
So if you are wondering how long you will have to wait on AT&T before a Windows Phone 7 device shows up, it should be reassuring to know it wont be any longer than anyone else.
See the Seminar documentation from June 24th here.