As with any OTA, not everyone will get it today. It will roll out over the next few weeks to all active stock GNex owners. Make sure you have well over 50% battery charge before attempting to install it. You can head into the Settings and Check for Updates, but that doesn’t always prompt it to pop up. Oh, and Wi-Fi is being mentioned as the only way to get the notification and download.
Good luck and happy updating. Lets hope the extra time to get it out solved any Verizon bugs they were facing.