The T-MobileSony Xperia Z3 is all set to get the Android 5.0 update as it has just been certified by the PTCRB. It’s common for updates to be certified by the PTCRB before it’s ready for a commercial release, so the rollout seems to be on track as of now.
The Android 5.0 update for Sony flagships from 2014 have started rolling out recently, so it was only a matter of time before T-Mobile sent out the update. Verizon also has a variant of the Xperia Z3 (known as the Xperia Z3v), so those users should expect an update sometime soon as well.
The update brings the build number 23.1.C.0.381 from 23.0.D.1.123. The update should begin rolling out in a few days from now, so don’t expect an OTA notification to hit your device right away.