It appears that we have an explanation as to why the Android 4.4 KitKat update for the Nexus 4, Nexus 7 and Nexus 10 devices is taking so long to roll out. It has released a new build, version KRT16S, which includes unspecified bug fixes as well as the usual performance and stability improvements. This would suggest that it slowed down or even halted the initial deployment to fix some issues.
Those still waiting for the update should now see Android 4.4 KitKat KRT16 hit their devices in the near future. Those fortunate enough to have already received the older update should now soon get this small maintenance fix as well.
The respective binaries and factory images have also been updated.
It remains to be seen if the Google Nexus 5 will also receive this updated build. For now at least, it appears set to remain on the slightly older KRT16M build.
Update: Reports are now starting to pop up online of Google starting to update the Nexus 4 along with ones for its Nexus tablets. As expected, it is the KRT16S build.