The Android 4.3 update for the international version of the Samsung Galaxy S III includes support for the Galaxy Gear smartwatch, and a change in the core UI to the one found on the Samsung Galaxy S4 and Samsung Galaxy Note 3.GPU drivers have been updated and a new Samsung virtual QWERTY is included. S-Voice is now the version from the Galaxy S4 and there is a whole new lockscreen. You will also notice a number of other changes.
Enjoy Android 4.3 while you can, because a leaked document last month revealed that Android 4.4 will be coming to the GT-I9300 sometime in March or April.
source: SamMobile via AndroidCentral