Motorola's David Schuster recent came out on Google+ to mention that the company is now soak testing Android 6.0 Marshmallow for the Moto X Pure Edition:
I'm pleased to announce that today we are starting the soak test period of Android 6.0 Marshmallow upgrade for the 2015 Moto X Pure Edition (3rd Gen) in the US. We will monitor the soak for next week and with good results, proceed to full launch.
The soak test period, which means that certain devices will be receiving the update early to test its reliability, will last about a week. Assuming nothing goes wrong, a full launch will follow.
Motorola is known as being one of the fastest third-party manufacturers to update their devices to the latest version of Android, and it seems they're maintaining that reputation this year.
The latest Android distribution numbers (from last month) show Android 6.0 Marshmallow on just 0.3% of devices, and that data is expected to be updated at some point today without much improvement.