Although the new Nexus 5X and the Nexus 6P were first devices to have the Android 6.0 Marshmallow OS, or precisely ship with the Android 6.0 OS, these devices are yet to reach their first customer, so it appears that the Nexus 5, Nexus 6, Nexus 7 (2013), Nexus 9 and the Nexus Player will be among first devices to get the new OS.

As expected earlier, the Nexus 4, the Nexus 7 (2012) and the Nexus 10 are not on the list and there is no word if these devices will be getting the Android 6.0 Marshmallow update at all.

The update will be rolling out in stages and the time-frame will depend on the carriers. In case you don't want to wait for the OTA update, you can always download the proper factory image available at Google's developer page.