The Galaxy Nexus will not be receiving the Android 4.4 KitKat update but as per Google Support the Nexus 4, Nexus 7, and Nexus 10 will be receiving the Android 4.4 update in the coming weeks and within two weeks time the above three Nexus devices would receive the Android 4.4 KitKat update. Apart from Nexus devices, the Android 4.4 KitKat update will be available for a list of other devices in time. Kindly take note that developers can begin coding as the SDK for Android 4.4 KitKat is live.
With the launch of the Redmi K20 that has come in the spotlight now, the Mi A3 could be delayed. We feel it should come sometime soon though and will be based in the upcoming Mi CC9 in China.