The Nexus 5 support page on US carrier Sprint indicates that the update will begin rolling out today, April 14th. 

google now nexus 5 Googles Nexus 5 to receive Android 4.4.3 update starting today

Android 4.4.3 has been said to be under testing with Google employees, and it looks like the update could be ready to start rolling out to Nexus devices.

Sprint’s support page for the Nexus 5 doesn’t actually say it’s Android 4.4.3, but given all the talk about the new build in the rumor mills recently, it’s probably the update the carrier is talking about. The changelog doesn’t go into much detail, only saying that the update enables “Sprint Spark band 26 and band 41″ and includes “Misc Android updates”. Rumors have said that 4.4.3 focuses solely on bug fixes, which is probably the reason the update’s changelog doesn’t give much in the way of useful information.

Android 4.4.3 is expected to fix multiple issues, including heavy battery drain because of background activation of the camera by apps, Wi-Fi and Bluetooth connectivity drops, and more. The update is scheduled to roll out in batches between today and April 21st, and in addition to the Nexus 5, we’re likely to see 4.4.3 arrive on the Nexus 7 2013 and Nexus 4 in the not-too-distant future.

Source: Sprint