Nexus 6 is getting Android 7.1.1 Nougat update once again3
Earlier this week, Nexus 6 had started to receive the long-awaited Android 7.1.1 Nougat. The update weighs in at around 370MB and it probably includes one of the latest security patches (July or August).
Obviously, in order to update to Android 7.1.1 Nougat, your Nexus 6 must be on the most recent Android 7.0 Nougat build that Google released. If you happen to be on the previous version of Android 7.1.1 Nougat, the one pulled by Google, then you'll have to flash back to the main update track.
Also, don't wait for other major Android OS updates like Android O since Nexus 6 is already reaching its EOL (end of life) status, so it's unlikely that it will get any new software upgrades in the future.