There is a lot of talk right now about Android 7.0, which is also known as Android N or Nougat. Even in light of Nougat, there are a lot of talk about Android devices that are still new but don't have Android M (also known as Version 6.0 or Marshmallow). Such is the case with HTC, and this is the latest news about Android M 6.0 Marshmallow and Android Nougat Release Date for HTC One M9, One M8, and HTC Desire Series on Sprint, T-Mobile, Verizon, US Cellular, and AT&T.
Well, if you know anything about HTC, the company was pretty good about getting Android Marshmallow out to its consumers. For example, the HTC 10 has, right out of its packaging, Android M. As for the flagship from the past two years, they are pretty much covered. This means that the HTC One M9 and the HTC One M8 is available, no matter what carrier you have.
There are reports about some of the non-flagship phones like the HTC Desire 820, HTC Desire 816, and the HTC Desire Eye are getting the update in some regions, according to Tech Radar. There are also reports that the HTC One M8 Eye could have the upgrade, as users in India have been receiving it. If this is true, then the upgrade should be coming to devices such as the HTC One M8s, HTC One M9+, HTc One ME, HTC One E8, HTC Butterfly 3, and the HTC Desire 826.
It is possible that the upgrade could be available on your newer HTC device already, but one carrier for the same phone and yet not on another, which has become a pattern for Android rollouts. If you have a recent HTC device, you might already have access to Marshmallow already, especially if you have a flagship. Just go to "Settings" and "System Update" to see if you can download the Over the Air (OTA) upgrade now.
As for when the release date for Android Nougat is coming, there is some news on that as University Herald reports that the Android Nougat update will be coming to the HTC 10, HTC One M9, and the HTC One A9. Considering that HTC guarantees that their flagships from two years ago will receive the upgrade, it is not likely that the HTC One M8 will receive the Nougat upgrade. As for the other non flagship phones, there doesn't seem to be any word on that.