Update: The files have now been removed from the servers preventing users from using this trick. However, users in our forums have set up a how-to guide to still make this happen if you are interested. You can find that guide here. Thanks, Hilmar, for the tip
Starting last night reports started circulating in our forums that the update is indeed available, but only on the Windows Phone Recovery Tool (WPRT) servers. This caveat means the update is not available over-the-air, but it may be coming in the future.
Windows Central has not yet confirmed the update on our phones, but some users have reportedly flashed their devices with the update through WPRT with success. Any user can run this Microsoft app to restore their phone from Windows 10 Mobile and go back to Windows Phone 8.1. It should be noted that this process obviously wipes the phone and all information on it. As such, you will want to have all your photos, music, and documents properly backed up.
Update 2 brings some notable changes mostly to the camera as users can take advantage of the faster Lumia Camera 5 app. That app results in faster photos and some advanced features like Rich Capture (HDR).
There is no word if and when AT&T will push the update officially. However, as we are nearing the official unveiling of Windows 10 Mobile in the coming weeks, we would not be surprised if AT&T ties this update into that one. Some reports suggest that Windows 10 Mobile's official update requires Denim, and this is likely part of that process. It is plausible that Update 2 won't come out as a separate update, but instead will be part of the update process to Windows 10 Mobile.
If you don't want to wait for anything over-the-air, you can use our restore guide on how to use WPRT.
Thanks, Allan R., for the images