Sony has recently started rolling out the Android 4.3 Jelly Bean update for the Xperia Z1 and the Xperia Z Ultra. The Android 4.4 KitKat update for both the devices is said to fill in a bit later. The Android 4.3 Jelly Bean update brings in a lot of changes.
To the Xperia Z Ultra, Sony has added the Smart Social Camera that was previously added to the Xperia Z1 through this update. Sony has also introduced Xperia Themes with good support for downloadable user interface packs and kindly make a note that the update is now rolling out to both the devices and should be available for download shortly.