HTC VP Mo Versi took to Twitter this morning to inform owners of the company's plans for the One M9's Marshmallow update, as well as the all-new A9's incoming bump to Android 6.0.1 (it ships with 6.0). Specifically, both devices can expect their respective software upgrades some time this month if all goes according to plan.
Lots of questions on this, so quick update: M9 unlocked Marshmallow OS update and A9 6.0.1 (with updated emoji) is on target for this month.
The unlocked One M8 is already getting Marshmallow, so while it is a bit odd that the newer M9 will be getting it later, at least it won't be that much later.
As for the A9, HTC has promised the device will receive any Android OS version update within fifteen days of the first Nexus device that gets it. Android 6.0.1 factory images just became available this morning (OTAs start today, too), so HTC theoretically has until December 22nd to make good on that promise.Correction: It turns out HTC actually later asterisked this promise as fifteen business days. This gives them until December 25th or 28th, depending on how they choose to count, and depending on whether they mean US business days, in which case the Christmas holiday may technically extend that out to the 29th. Technicalities, aren't they great? (Update: HTC says their commitment deadline is December 28th for Android 6.0.1 on the A9 - you heard it here.)
We'll be on the lookout for official notice of the M9's Marshmallow rollout, and will let you know when we see or hear anything. As to carrier variants, well: we've got nothing. Hopefully information around those devices will materialize once the unlocked version's update starts hitting devices.