Sprint is rolling out a brand new Android 4.4.2 KitKat OTA Update with the NJ1 code set as firmware version. It is not a major upgrade, as it adds new calling elements and various bug fixes, all these changes should offer you a much more stable Android environment.
The changelog of Android 4.4.2 NJ1 upgrade for Sprint Galaxy Mega 6.3 says that it brings HD Voice Icon support, Google Security Patches and International Wi-Fi Calling support. Besides all these changes you should get various stability improvements and security fixes that should improve the overall performance of your device. No other major changes have been listed, so you can tell us in comments after the new firmware version is flashed on your device.
The International Wi-Fi Calling feature support for Galaxy Mega 6.3 will now allow you to successfully use Sprint number when you’re not in the country. The new update is being released in phases, so you should be getting the update before the end of the month. In case the new NJ1 Android 4.4.2 KitKat firmware update doesn’t arrive before the end of this week, then you shouldn’t panic as it will surely be available for installation next week.
If the update notification hasn’t been displayed on your device, then you should go to Settings> General> About Device and use the System Updates section in order to search for new KitKat firmware builds download availability. If the new update is ready to download you should make sure that you’re using a Wi-Fi connection to install the files. The update installation process will then complete automatically.
Note that the new Android 4.4.2 KitKat NJ1 build will only be sent for Galaxy Mega 6.3 Sprint devices that are running stock ROMs, you will not receive any new files in case you’ve installed any custom ROMs nor in case you’ve applied any other customizations.