Older devices such as the Galaxy S2, Galaxy Note 2 and newer ones such as the Xperia Z1 all have the ability to run Android 4.4 KitKat thanks to Cyanogen Mod 11.
The ROM has made its way to many of today's popular devices since the beginning of 2012 and hit those other handsets earlier this week. The full list to devices to receive CM11 can be found here. Some of these handsets will never see an official Android 4.4 KitKat update from Google.
Some new experimental builds of CM 11 are also available for the Xperia Z1 and the Google Play Edition of the Xperia Z Ultra. The team stressed the difference between the builds found on the GPe and non-GPe Z Ultras and urges users to install the correct versions on each one.
The Android 4.4, KitKat update for AT&T Galaxy Note 3 and Galaxy S4 users leaked onto the internet at the end of last month in the form of two new ROMs.
The new firmware was posted up by XDA Developers forum member Designgears. This update is not the final version that will be rolled out by AT&T later this year therefore the firmware for both versions has its share of bugs and other issues.
The Galaxy S4 has a bug that forces users to reboot their device when playing a video. Users will have to flash a new bootloader if they decide to go through with the upgrade which means they will not be able to return to Android 4.3.
The existence of both of these ROMs suggests that the official AT&T update for the Galaxy Note 3 and Galaxy S4 should be rolling out shortly.