Google has just posted the factory images and binaries for Android 4.4.3 for all current Nexus devices, including the Nexus 4 and Nexus 5 by LG, the 2012 and 2013 Nexus 7 by ASUS, and the Nexus 10 by Samsung.
Here they are:
We are still waiting on the 2013 LTE Nexus 7, but compared to the last time Google released an update to Android, this is much better. (If you remember, the Moto X got it before many Nexus devices, and Google Play Edition devices were all over place. It was a mess.)
It’s possible that Verizon is forcing Google to wait until it approves the update for the LTE Nexus 7. When Google released the device without Verizon’s approval back in 2013, Verizon took its sweet time approving the software, and then made Google release an OTA update to satisfy it.
In any case, if you want to install the update right away, Android Police has a great tutorial on how to do that using a factory image without erasing any of your data. Otherwise, you can wait for the update to appear on your phone automatically.[Google]