Though the international variant of the Sony Xperia Z was recently upgraded to Android 4.4.2 KitKat, those in the U.S. aren't as fortunate as T-Mobile has only finally gotten around to updating the waterproof handset to Android 4.3 Jelly Bean. T-Mobile customers should begin getting their update notifications now. This brings the firmware build to 10.4.C.0.814 for the Xperia Z on T-Mobile.
The upgrade is a jump from the current Android 4.2.2 Jelly Bean build that is current on the Xperia Z at this time.
If you have a T-Mobile-branded Xperia Z in your hands, have you gotten your update notification to upgrade the software yet?
Source: Xperia Blog