Sony Mobile has confirmed that the Android 4.1.2 Jelly Bean update is now available for Xperia S, SL, and acro S. The Jelly Bean update for the three Xperias got certified last month. The Sony Xperia ion is next in line to receive the update.
The Sony Xperia S, SL, and acro S users would get a notification regarding the firmware update. The phone will notify you when the firmware is available or you can also check it through Sony PC suit. The update would be available Over the Air (OTA) (depending on the regions and carriers) and via PC Companion on Windows/ Bridge for Mac.
The Sony Xperia P, Xperia go and the Xperia E dual got the Jelly Bean update last month. And now Xperia S, SL, acro S got the update, Xperia ion update will follow.