Samsung promised that they’ll be bringing some of the features in the Galaxy S4 to the previous flagship Galaxy S III. SamMobile has leaked firmware (I9300XXUFME3) for such device and shows the GSIII running Android OS 4.2.2.
Some of the new features are coming, such as the lockscreen widgets and effects (Ripple and Light), enhanced screen modes (Adapt Display and Professional Photo), new Settings UI, voice controls and the new S Voice. Of course, some of the most notable features are not making it into the GS III due to its hardware limitations, namely Air View, smart TV remote app and some camera features like eraser mode.
The reputable site says the OS is still in testing and Samsung is expecting an official Galaxy S III update sometime in June. SamMobile has made it available for download via their site, but install at your own risk.