The latest version of Lollipop (Android 5.1.1) is finally starting to rollout to devices. To go along with that, Factory images for 5.1.1 (build number LMY47V) on WiFi versions of the original Nexus 7 (2012), Nexus 7 2013, and Nexus 10 tablets are available on Google’s factory images page.
This will let you manually update your device immediately before it starts rolling out OTA. Here's the link: Factory Images for Nexus Devices - Nexus Files for Developers Google Developers