Android Marshmallow factory images are live for Nexus devices
You can grab the the factory images right now and flash Marshmallow to your Nexus 5, 6, 7 (both Wi-Fi and LTE models, 2013 only), 9, and Player. Follow our walkthrough if you want some direction about how to do this.
If installing Marshmallow yourself is too intimidating, you can always wait for an over-the-air update directly from Google. However, it can be anywhere from a few days to a couple of weeks before your device actually gets the new software. So settle in and be patient if you don’t want to install it yourself (or don't want to wipe the data on your device).
The impact on you: This is why you go Nexus: the latest flavor of Android as soon as it’s ready. While Samsung, LG, and others have improved their timeliness when it comes to Android updates, you’re still going to wait weeks, or more likely months, to get the newest version on your phone or tablet. If you’re feeling the itch for a new phone, you can pre-order the new Nexus 6P or Nexus 5X, which both run Android 6.0 right out of the box.