Google has uploaded the factory images based on the recent release Android 4.1.2 for Nexus 7 and takju variant of Galaxy Nexus smartphone. These images can now be downloaded from Google Developers website.
These images can be used by the Nexus 7 and Galaxy Nexus owners to flash on the latest Android version on their devices. Guides are available on XDA or use one of the all-in-one utilities.
There is still no official word on when can we see the OTA update roll-out for Galaxy Nexus, we expect it to start anytime now.