As with all Google updates, this one will be rolling out gradually over the next few days. We should have the OTA URL at some point so you can update manually, but you're going to be waiting a while for the mobile data versions of the Nexus 7. Those updates will take a little longer. Likewise, the Nexus 4 update has not started yet.
https://productforums.google.com/forum/#!category-topic/nexus/other-discussions/nexus-5/f1EOEtihDxI
Source:
http://www.androidpolice.com/2014/1...d-for-the-nexus-5-6-7-2012-and-2013-9-and-10/