Canadian carrier Rogers is expected to push the update in early 2014
Almost all Samsung smartphones that have been confirmed to receive Galaxy Gear support have been updated to Android 4.3 Jelly Bean, but one device has yet to receive the upgrade, Galaxy Mega 6.3.However, a Rogers internal note published by MobileSyrup confirms that Samsung Galaxy Mega 6.3 will receive the Android 4.3 Jelly Bean in January.
“Note: In order to be compatible, the Samsung Mega requires a software upgrade that is expected to be available as of January 2014.”
Even though we don't have confirmation that Galaxy Mega 6.3 will get the update in other countries as well, it's safe to assume that everyone will be able to update to Android 4.3 Jelly Bean around the same timeframe.
More details on Android 4.3 for Samsung Galaxy Mega 6.3 are expected to leak within the next few weeks as we're getting close to release, so stay tuned for more info on the matter.