With the rollout of Android 6.0 (also known as Android M or Marshmallow) about two months ago, Google has been working with smartphone manufacturers to see that their newer devices get the upgrade. After coming to the newest of Google's own Nexus series, it is slowly trickling down to other manufacturers like the popular HTC. This is what is known about the Android L Lollipop and M Marshmallow Update Release Date for HTC One M7, M8, M9 for Verizon, Sprint, T-Mobile, and AT&T.
So far, the latest news about the HTC upgrade to its flagship series of phones comes from Know Your Mobile. The software update build for the handset has appeared in a Bluetooth SIG certification for the One M8, which means that certification for the connectivity protocol is nearly ready.
Considering that the HTC One M8 is one of two phones that is slated to receive the Android 6.0 update by the "beginning end of 2015", it shouldn't be surprising that it is almost ready. The plan for this comes from HTC on Twitter, and the other phone that is slated to receive the update is HTC's current flagship, the One M9.
Other devices that are scheduled for the update include the One M9+, One E9+, One E9, One ME, One E8, One E8 EYE, Butterfly 3, Desire 826, Desire 820, and the Desire 816. The One M7 did not make the cut, as it is an older phone.
HTC is usually good about promising the Android upgrade to their devices within 90 days after the initial rollout. There was a missed deadline last year when it came to Android 5.0 (also known as Android L or Lollipop). Some of the devices listed above are going to be getting Android 5.1.1, but some might skip that and go straight to Android 6.0.
What is interesting about the HTC One M8 is it is possible to get the upgrade now. It isn't available as an OTA update, but a new updated CM13 series CyanogenMod custom ROM has been made available, according to the International Business Times, which has step-by-step instructions. This procedure is very technical and should be performed by someone who has knowledge of rooting or manual software installation, and if it is not followed properly, there is a risk in doing permanent damage to the HTC handset.
Of course, if you want Android 6.0 on an HTC device, there is an easy way. Just get yourself an HTC One A9, not to be confused with the HTC One M9. For some reason, the company decided to release an all-new model, but it is not known if this is some trial flagship phone of some type. The company is good at releasing their new phones around Mobile World Congress, which will probably be where they will unveil the HTC One M10, assuming the company still wants to use this series name.