Google and Android announced the update via their respective Google+ and Twitter pages. Both generations of Nexus 7 and Nexus 10 can now be updated to Android 4.4 KitKat Operating System. However, the update is only for the Wi-Fi version. The update for 3G/4GLTE variants will be released soon. This also includes the Nexus 4.
It has been confirmed that Galaxy Nexus will not be updated to the latest Android KitKat OS.