We recently heard that the Android 4.3 update was being tested on the Samsung Galaxy S4, plus some other devices, and now it would appear that we have some more details on the galaxy S3 Android 4.3 update.
According to what we heard yesterday the Galaxy S4 is expected to get Android 4.3 some time in October, and the Galaxy S3 Android 4.3 update is expected to land in November.
As well as the new Android 4.3 for the galaxy S3, the Galaxy Note 2 is also rumored to get the update in November, of course this has yet to be confirmed by Samsung.
Source Android Community