It has not been very long since Google dropped the latest version to their Android operating system, named the Nougat 7.0, and HTC is not even allowing that news go cold first before they have started to announce when they would be pushing some of their own devices to this whole new level.
With what they have let loose, they are planning to lease out the update to the Nougat to their smartphones, especially the HTC 10 line-up, sometimes in the fourth quarter. This means that the earliest time we could start to see the bump is the month of October while the latest is December. After the HTC 10 would have gotten it, they would then start to consider the users of the HTC One M9 and One A9.
From the official information, the variants of these devices that would be getting the push first are the unlocked variants of these three smartphones and after that, you would be getting yours if your device is being run on a carrier network. If you recall, HTC has already announced the push to the Nougat to these devices as far as June and the fact that they are still keeping to their word is a laudable thing.