For the Samsung Galaxy S4 I9505, Sammobile has received a pre-release firmware of Android 4.2.2-running TouchWiz. There is a build number I9505XXUFNNNA1 at release.

The build is stable enough to be used as a daily driver but still shaky here and there. In the February to March window, the final update is expected to be released.

Samsung Galaxy S4

The most notable changes are a camera shortcut on the lock screen, the white status bar icons (from green), and an improved and performance boost landscape keyboard.

Samsung Galaxy S4 Picture

Flashing the firmware does include risks of bricking but is pretty straightforward. You need to download the around 1GB file and then through Odin, flash it in Downward mode.