When it comes to updates, the Nexus range of devices has always been considered to be the first in line. This is understandable due to the nature of the Nexus affiliation with Google and is actually one of the selling points to owning a Nexus device. In fact, just before this year's I/O event, rumors began circulating that Google were planning to extend the update priority with Nexus devices by making sure they receive guaranteed updates for a set period.
Well, this morning, reports emerged noting that Google had started sending out an update to the Nexus 5 and the Nexus 6. This update was designed to be a security update and one which would combat the Stagefright vulnerability which has been making the headlines so much recently. In fact, on a tangent, it seems a number of carriers have been releasing updates to various devices to combat the Stagefright vulnerability today too. However, in terms of the Nexus update, it was assumed this was a solitary update for the specific security reason.
However, Google has now announced that Nexus devices will begin seeing regular updates each month as a security measure. The announcement (source link below) details that the updates will begin today, August 5th, and presumably have already started with the already mentioned Nexus 5 and 6. Although, the devices which will see a monthly update landing is much wider. Included in the monthly update schedule is the Nexus 4, Nexus 5, Nexus 6, Nexus 7, Nexus 9, Nexus 10, and Nexus Player. As such, if you own any of these devices, you are likely to see the monthly updates beginning anytime in the next few days. Google also confirmed that the updates will be released to the AOSP at the same time. The current update looks to fix issues raised through July 2015 (includiing the Stagefright vulnerability). Closing out the announcement, Google also confirmed that they will be sending major updates to all Nexus Devices for two years and security patches for three years (from the initial availability of the updates) or 18 months from a purchase on the Play Store. Whichever is the longest. This last point is in line with the rumors we heard back in May about the guaranteed updating.