According to WPC, AT&T will start updating their Windows Phones to Mango on Tuesday. They will be sending out the update for all three of their Windows Phones, which are the HTC Surround, LG Quantum and the Samsung Focus.
Now it does get slightly more complicated as there are two different versions of the Samsung Focus. If your running the Samsung Focus with v1.3 will get the update on 27/9. If your running the phone with v1.4, then you will have to wait until the end of October to get the Mango update.
The Dell Venue Pro will be updated by Dell directly and so we are looking to them for information. So everyone else will get the update either sometime next week or by the end of October. This is something to look forward to as the update will be with most of you AT&T users in a few days time.