It was just yesterday evening that we complained about Google's apparent inability to get updates rolled out to the 2012 and 2013 Nexus 7s with cellular data, and now here we are. Google has posted sytem images based on Android 5.0.2 for both devices. How about that?
These images will require that you have an unlocked bootloader and ADB set up on your computer. The default functionality is to wipe your device, but you can edit the batch file to remove the wipe command, if you want.
The images for nakasig and razorg have build number LRX22G, which dates back to October 22nd. There are also driver binaries available for these devices, which was probably the reason for the delay. No OTAs have been sighted yet, but they won't be far off now that the system images are ready.
I'm not saying we're definitely responsible for making Google release the factory images, but you can totally say that if you want.