Unfortunately, this is sad news, but according to what reported Sammobile, Samsung officially announced that the Samsung Galaxy S3 and Galaxy S3 Mini devices will not receive Android 4.4.2 KitKat update.
Galaxy S3 was sold with Android 4.0 Ice Cream Sandwich out of the box, which was later updated to Android 4.1.2 Jelly Bean. Last update received by the terminal, was Android 4.3 Jelly Bean.
Galaxy S3 Mini is currently operating the Android 4.2 Jelly Bean and it will probably be the last operating system version for it, because, at this moment, there are no plans of updating it to a newer Jelly Bean build.
Samsung’s official statement confirms what we already knew, namely that the amount of RAM on the device does not guarantee good performance. Galaxy S3 and S3 Mini have 1GB of RAM on board, which makes it impossible to efficiently support the Android 4.4.2 KitKat upgrade.
The declaration of Samsung, it is pretty straightforward and objective that you can read it on sammobile website.
If you use a Samsung Galaxy S3 3G you have the possibility to flash on your device a different custom Android 4.4.2 ROMs. This operates because the Android 4.4.2 KitKat OS can run with 512 RAM although that is possible with stock Android characteristics, but the new update from Samsung includes many other upgrades designated for their bloat apps.
Therefore, you have the possibility to choose from many custom ROMs like CyanogenMod or Paranoid Android launched to try Android 4.4 KitKat on your device.