Leaked images show a new unofficial Sony device called the C5303. This device has the same power button as the Xperia Z and the Xperia ZL and has on-screen navigational buttons on the bottom. There is no size known yet, but it would probably have a 720p display arround 4.3”. It'll run on Android 4.1 Jellybean.
According to leaked benchmarks, the C5303 has a 1,7 Ghz dual-core Qualcomm S4 Plus Turbo processor and a Adreno 320-gpu which is the same one used in the Xpera Z.
This device will probably be announced on the Mobile World Congress in Barcelone in february.