Android 4.4.1 update in testing right now, could be released soon
Server logs have appeared that show the 4.4.1 update running on the Nexus 4, Nexus 5, and Nexus 7, but not the Nexus 10. Additionally, HTC ROM developer LLabTooFeR is saying that the HTC One Google Play Edition is going get an update to 4.4.1 (KOT49E) "in near future". We would assume that this would mean the update is also going to be coming soon to the Samsung Galaxy S4 Google Play Edition.
Obviously, we don't know exactly what to expect from the update, but we're hoping that the audio issues that have been reported with the Nexus 5 will be solved.