Now that Google has started to roll officially out the latest version it operating system with Android M (also known as Android 6.0 or Marshmallow), it is now a matter of time before it will be available to newer versions of Android devices. This is the case for Motorola devices like the G series (like the G3 and G2), the X Series, but sadly not the E Series. This is what is known of the Release Dates to those Moto devices on carriers like Verizon, AT&T, T-Mobile, and Sprint.
According to the Latin Post, the Moto X Pure Edition, released about a month ago, will be the first of Motorola's device to receive Android M, and it will probably arrive sometime in November. This was to be expected, as Motorola has unveiled a list of what phones will be receiving the Marshmallow update, and it also includes the 2015 Moto X Style (3rd gen), 2015 Moto X Play, 2014 Moto X Pure Edition in the US (2nd gen), 2014 Moto X in Latin America, Europe and Asia2 (2nd gen), DROID Turbo, 2014 Moto MAXX, 2014 Moto Turbo, and Nexus 6.
You might notice certain Motorola devices that are relatively new that didn't make this list. For example, the Moto G 1st Generation, the 2013 edition, will not be getting the Marshmallow update, but it did have its final update to Android 5.1.1. The same applies to the first generation of the Motorola X, as well as the entire E-Series.
Motorola has announced that the Moto G3 and Moto G2 will also receive Android 6.0 soon, but not as fast as the Moto X Pure Edition. So when will the update be coming for Motorola's G3 and G2 series? According to Android Standard, the G3 is expected to receive Marshmallow before the G2. This was to be expected, as most rollouts of new versions Android tend to favor the latest models, and then trickle down to the older models afterward.
It is anticipated that the retail editions of the Moto G3 may get the update in November. However, some regions, like the US Carrier locked versions of the Moto G 3rd Gen may receive the Marshmallow update in December.
As for the G2, Motorola may start the "soak test" for Marshmallow in India, which could result in a delay of the G2 not receiving the Marshmallow update until the beginning of 2016.
Once the rollout becomes active, it is only a matter of waiting. It does seem positive that the G3 will be getting its implementation before the end of the year, but this might depend on the carrier. Occasionally, some carriers will have it sooner, and some will have it later.