There is convincing intel that Google is currently working on build KTU65 of a new Android KitKat update. The evidence, (in the screenshot above) appeared in a Google Code bug report for Chromium. It was uploaded by a Googler who was apparently testing the build on a Nexus 5. The KT designator definitely makes it a KitKat update, while the number at the end is a date identifier.
It is suspected that this update is meant to curtail some bugs, especially the camera-battery drain issue that is plaguing a few users. We will keep you updated when more info emerges.
originally written by dgstorm