HTC's Versi says Android 6.0 will hit carrier branded HTC One M9 in Canada during early 2016
We might actually have a clue as to when the update will arrive. Back in October, Canadian carrier Telus updated its software release schedule. The revision calls for the mobile operator to start pushing out Android 6.0 to the HTC One M9 on January 21st. Other Canadian carriers should start updating their branded One M9 to Android 6.0 at around the same time. Telus customers with the HTC One (M8) will be receiving Android 6.0 on December 17th.
Android 6.0 comes with Doze, which puts your phone into a deep sleep when it is inactive. Doze will disconnect apps from running in the background, and increases standby time by a large amount. The update adds contextual search with Google Now On Tap. The feature figures out what is on your screen and brings you information about it. Also part of Marshmallow is the new app permissions system, which allows you to give or deny permission on a feature to feature basis.
source: @moversi via MobileSyrup