While Lollipop is starting to show up on more and more devices, there are still plenty which haven't yet received the updated software. For those devices which have already been updated, the wait for some has transitioned into waiting for Lollipop's most recent version which is Android 5.1. The HTC One M9 is one of these phones. Earlier this morning it was discovered that AT&T's version of the HTC One M9 would be getting its update to Android 5.1 Lollipop starting tomorrow which puts it ahead of Verizon in terms of software upgrades but still behind the unlocked model, as well as the Sprint model which started showing up back on July 1st.
This will leave Verizon and T-Mobile as the last of the four major carriers in the U.S. to send this update out. The latest details from Mo Versi thanks to a tweet which went out earlier this morning in response to another user, state that T-Mobile and Verizon Wireless versions are "on track" for a release on July 20th. That's not too far out from now, roughly a week, (six days to precise) and assuming HTC is able to keep to that schedule and keep the carriers on schedule, most HTC One M9 owners should be updated to 5.1 Lollipop within ten day's time. That is assuming though that nothing goes wrong which pushes back the software update release, so users on Verizon and T-Mobile will just have to keep their fingers crossed.
Typically with these updates to the HTC devices, Mo Versi will end up stating the details about exact push dates, so it can be expected that he'll post another tweet when the update is ready to send out which will be one thing to watch out for. In terms of what to expect with this software version, Android 5.1 is mainly about bug fixes and improvements, but there are a few tweaks which come along with the software like camera improvements, and there should be some improvements to the software that help to control temperature of the CPU, something which has been a common complaint of some users on the processor over its launch period.