We’ve done quite a bit of work on reviewing the Android M and Android 6.0 Marshmallow developer previews. Today, Google announced that Android 6.0 Marshmallow will begin rolling out to Nexus devices next week.
Of course, Android Marshmallow will come in staged rollouts, which means that only about 1% of Nexus devices will receive the update next week and only another 25% will receive the update in the following week.
Of course, you can always flash the image on the device.
If you’re using a non-Nexus device, chances are that your OEM has a policy to update your device within 90 days, assuming your device was released within the last two years.