The update to Android 4.4 brings a number of new features including an improved UI, the merging of your MMS and SMS messages on Hangouts, support for closed captioning, the ability to remotely wipe your phone with Android Device Manager, an improved camera app, longer battery life and more.
Recently we showed you a leaked document that showed that the international version of the Samsung Galaxy S4 will receive the Android 4.4 update in January. Considering that the update will need to undergo some carrier testing, we could see Android 4.4 hit the Samsung Galaxy S4 in the states sometime after the turn of the year, hopefully by the time Q1 is over. Meanwhile, HTC One owners in the U.S. and the U.K. with a carrier branded model are supposed to be updated to Android 4.4 sometime in the first month of the year.
The Samsung Galaxy S4 Google Play edition and the HTC One Google Play edition are both starting to receive the Android 4.4 update
source: +Android, XDA via Engadget, AndroidCentral