Sony's official support page for the phone has just changed back, showing the Android 4.0 build instead of the Android 4.1.2. that showed on the page earlier. The tweet from Sony Mobile France reads "Xperia S: The deployment for 4.1.2 build has just begun for the first builds" when translated. They add that the update is being pushed out and other builds of the phone will be updated next week.
If you own the Sony Xperia S and received the update, let us know by dropping us a line in the box below.
source: Sony, SonyMobileFrance, XperiaBlog via AndroidCentral