Google is expected to update its Nexus devices today (Nov,12th). Well, the updates isn't rolling-out yet, However, the official Google Nexus 7 (2012) WiFi Android 5.0 Lollipop Factory image [LRX21P] has just been leaked online.
If you happen to own a 2012 Nexus 7 (Wi-Fi only) variant, you're lucky, you can flash the image below to your device and you won't need to wait for the Lollipop OTA update. We might see all other devices factory images online pretty soon following by the OTA.
File name: nakasi-lrx21p-factory-93daa4d3.tgz