With no announcement, Google is updating Nexus devices with Android 4.2.2 Jelly Bean. The new operating system is rolling out to the Nexus 7, Nexus 10 and Samsung Galaxy Nexus. It's also possible the update is rolling out to the Nexus 4smartphone. See also: Android 4.2 Jelly Bean FAQ: What you need to know.
A screenshot of the update on a Nexus 10, via Android Police, says: "This software update will upgrade your Nexus 10 to Android 4.2.2 Jelly Bean, which improves performance and stability."
Google hasn't given any further details of what the update contains but a Bluetooth A2DP audio streaming fix was promised in the version following Android 4.2.1. The update is relatively small at 47.6MB. See also: Android 4.1 (Jelly Bean) review
According to Recombu, the Google Nexus S, made by Samsung, will not be receiving Android 4.2.2 Jelly Bean or any further updates.
Going by the comments online very few users have been able to update so far. With no official word from Google on the rollout the only thing you can do is keep checking for available updates or wait for a notification. See also: How to manually upgrade an Android smartphone or tablet