A few Nexus devices have received updates to either the 5.0 or 5.1 build of Android Lollipop, but not all of them can expect to be upgraded to Android M when it is released.
According to Android Police, a reliable source who spoke on condition of anonymity said that Google is about to enforce a new set of rules that specifies the length of time that a specific Nexus phone will be eligible for operating system and system updates.
The source specified that each Nexus unit will continue to receive major system updates for two years after its release. Nexus devices are also covered with three years’ worth of security patches to protect them from vulnerabilities.
Alternatively, the source added, Nexus handsets will also receive security patches for up to 18 months after date of purchase from the Google Store or Play Store.
This means that some Nexus phones will no longer receive any update to Android M, Slash Gear concluded.
According to Slash Gear, the Nexus 4 and the Nexus 7 (2012) will no longer receive system updates but will receive security updates until the end of this year until this new rule set.
On the other hand, the 2013 version of the Nexus 7 handset can still receive OS updates until the third quarter of this year, and will continue to receive security updates until the first quarter of next year.
The Nexus 10 will also not receive updates, but will continue to receive any security updates until 1st quarter 2016.
The Nexus 5, 6 and 9 handsets will stop receive operating system updates after third quarter 2015.
The Nexus 5 will receive security updates until Q3 2016, and both Nexus 6 and Nexus 9 will receive system updates until Q3 2017.
There is still no official announcement from Google to confirm the deadlines and end-dates for system and security updates for Nexus updates.