XDA dev JanM RS has released an Xperia Theme based on the design of the next major Android iteration, dubbed “Android L”. The design elements include the Android L style buttons, colours and wallpaper. Quite a nice theme worth trying.
The great thing about the theme is that it works for non-rooted handsets as long as you are running Android 4.4.2 KitKat on your Sony Xperia device. If you want to give it a try, you can download the apk here and install as you would any normal Xperia Theme.
Update: Also see Ben Ling’s port of a similar Xperia Theme on XDA. This will work with devices on Android 4.3 and above, but requires root.