This evening, Google announced that a new build of Android 4.4 was going to push out shortly as build KRT16S. It’s a bug fixer, nothing more. An OTA update should arrive before long, and may even be available already on the Nexus 7 (2013) as a 3.4MB file. The Nexus 4, Nexus 10, Nexus 7 (2012) should also all see this update.
The factory image files and binaries for each have already been posted for all Nexus 7 variants, the Nexus 10, and Nexus 4. Go get ‘em.
The previous version of Android 4.4 that was available to these devices was build KRT16O.