While it has not been included in the Android Marshmallow beta testing, all indications are that the Nexus 7 (2013) will be getting the update once it is released next week. The 7″ tablet built by Asus certainly falls within the 3 year support window that Google has for their devices and given that specifications of the Nexus 7 (2013) meet the minimum criteria, there should be no reason it won’t be updated.
The strongest indicator came from Android Police’s Artem Russakovskii who posted on his Google+ that he has confirmation that the Nexus 7 (2013) will be getting Android Marshmallow. While
this isn’t 100% airtight (in other words, directly from Google), it does follow leaks and rumors that the 2013 tablet will get the update. As for when that will happen, that is a good question. It could well be next week with all of the other Nexus devices but could take a bit longer given we have seen no beta builds of Marshmallow for the device.
I personally am a big fan and user of the Nexus 7 (2013) and do hope it sees the Marshmallow update. As I put in my review of the device, it will likely be the last major update it sees but certainly has the chops to run it.
It should be noted that I’m referring to the 2013 version of the Nexus 7, not the 2012 version. The 2012 unit would struggle to run Marshmallow on its specs and it outside of the support window from Google. That said, you can almost certainly expect a Marshmallow based ROM from the developer community to be released for the Nexus 7 2012 as well as the Nexus 4 which also will not be updated by Google themselves.