HTC One M9 and One M8 was going to get Android 6.0 Marshmallow tied with AT&T. But now, it has been delayed as stated by the AT&T.
Now, the wait is a bit longer than the scheduled time. As per the, Mo Versi, HTC One M8 & M9 AT&T owners there’s been a slight delay on M OS. We’re in lab but looking at approval within the next couple weeks.
Already, AT&T is quite late as Sprint and Verizon has already rolled out the HTC One M9 and One M8.