I think I've read that Nexus 4 will not receive monthly security updates any more. But I couldn't find the official information, other than this general page. Can you help me with this ?
Nexus devices will also receive updates for security issues documented in our Public Nexus Security Bulletins for at least the following periods:
Three years from when the device first became available on the Google Store
Or, 18 months after the device stopped being sold on the Google Store
As Nexus 4 was released on November 13th 2012 it is outside this time frame and will likely not receive many more monthly updates.