Technical approval from the carrier has been given, rollout to begin soon
T-Mobile HTC One Owners! We have received technical approval for 4.4 OS + Sense 5.5! Expect the OTA out shortly! Thank you for your patience— Mo (@moversi) February 21, 2014
We don't expect much deviation from the standard 4.4 and new Sense we've seen on other phones — and that's a good thing because it runs pretty well. Keep your batteries charged, and keep checking for that update. When it hits, holler!