According to leaked information from Samsung R&D in India, Samsung is simultaneously developing Jelly Bean 4.2.2 and 4.3.0 updates, and the former could be dropped altogether if Jelly Bean 4.3 is officially announced this week (http://www.gsmarena.com/google_announces_an_android_event_on_july_24-news-6402.php) by Google.
These rumors from last week garnered a whole lot more credibility thanks to the provided leaked image which allegedly shows a Galaxy S III running on a 4.3.0 Jelly Bean test build.
(http://cdn.gsmarena.com/vv/newsimg/13/07/galaxy-s3-43/gsmarena_001.jpg)
Word is that development of the 4.3.0 update is also underway for the Galaxy S4 flagship, as well as another yet unannounced device, possibly the Galaxy Note 3.
It's still unknown what kind of features the 4.3 Jelly Bean update will to bring - or when, for that matter - but if the above leak is any indication, the announcement is imminent!
Update: Seeing as how the kernel version and build date in the image are the same as those found on Android 4.1, then either the software is not finalized, or the build.prop has been tweaked to show a different Android version.
Source (http://temefy.com/samsung-galaxy-siii-captured-running-android-jelly-bean-4-3-test-build)
GSMArena.com