If you’re still rocking the original HTC One M7 on T-Mobile, the wait is almost over for your turn to get the latest version of Android. Confirmed on Twitter by Mo Versi, HTC’s VP of Product Management, the update will start this coming Tuesday, March 10th.
HTC One (M7) T-Mobile Owners! We've received technical approval on the L OS and OTA will start on Tuesday. #htcadvantage
— Mo Versi (@moversi) March 7, 2015
As with all OTA updates, it will come in staged rollouts, so you may not get it right away, but just keep hitting that check for updates button. Or keep an eye out on XDA or elsewhere for a manual update file to be posted.