The Moto X 2nd Gen unlocked version is getting Android 6.0 Marshmallow update, the update size is 884MB, and has been spotted in U.S, Canada, Brazil, India and the U.K.
The Marshmallow brings new features to the phone such as Google Now on Tap, Adoptable Storage - you can integrate MicroSD card with main internal storage, improved app permissions, Doze mode that increases your Phone's battery life.
If you haven't got update notification then don't worry the update is rolling out in stages, so it can take time to the update to reach your phone. To manually check the update Go to Settings>About Phone>System Updates. Be sure to connected to Wi-Fi and make sure that battery is charged at lest 60%.