One of the issues with the newest version of Android is that Google will give it to their own Nexus devices first, and then it will slowly roll out to other Android devices, like the ones made by Motorola. Motorola is usually pretty good about getting fast updates to its subscribers as the company doesn't add much to the stock Android, and the company is pretty determined to bring Android version 6.0 (also known as Android M or Marshmallow) to its subscribers very soon. This will hopefully the case of the Moto series such as the Moto X 2nd Gen, 3rd Gen; Moto G 2014, 2015, and Moto E on subscribers like Verizon, AT&T, Sprint, US Cellular, and T-Mobile.
So far, the reports of Moto series phones receiving the update are few and far between. Tech Blorge reports that the update for the Moto X and Moto X Style first went to Brazil and India in mid-November, and then Moto X Pure users were receiving Marshmallow on AT&T, Sprint, US Cellular by December. There are also reports of the Moto X, 2014 Moto X, and Moto G receiving updates in some places like India and Australia.
It is clear that Motorola wants to put Marshmallow on as many of its devices as it can, and this list the Motorola wants to upgrade to Marshmallow includes the X Series like the Moto X 2nd Gen (2014), the Moto X Pure Edition (2015), the Moto X Play, the Moto X Force, and the Moto X Style. Also included is the G series that includes the Moto G Turbo, 2014 editions of the Moto G and Moto G 4G, as well as the Moto G 3rd Generation from 2015. Then there is the E series, which wasn't expected to receive the Marshmallow upgrade at all, but the 2015 edition will.
Other Moto products to receive Android 6.0 include the Moto Maxx, Turbo, DROID Turbo, Moto DROID Turbo 2, and Maxx 2. The Droid Turbo is on the list to receive the updates, and this Verizon exclusive available phone has been reported to get an over-the-air update of Android 6.0.1, by Verizon employees only for a limited edition red version.
As mentioned before, the company really, really wants to break Marshmallow to its customers soon, but they don't have a set schedule for it. They do encourage their customers to "stay tuned for more details on upgrades for specific devices", and Motorola users should check their System updates to see if the upgrade is available. Even Marshmallow does come to these select Motorola phones, there could be a delay depending on the subscriber like Verizon, Sprint, AT&T, T-Mobile, and US Cellular.