It seems like that the Samsung Galaxy Smartphone lineup on the AT&T are soon going to get an Jelly bean 4.3 Update. The latest Android firmware for AT&T versions for various smartphones has made the rounds on web.
Here is some part of the change log, i.e.., some of the new features that the update would be bringing in to your smartphone.
According to the rumors, AT&T would be rolling in the updates for S4 by the end of October. Where as on the other hand , S3 and Note 2 will be getting the Android 4.3 treatment in November. Galaxy S4 Active would be getting it in beginning of December.
Also note that pre released firmwares can be downloaded via the source links below.