Sony didn't announce its Xperia Z4 smartphone at MWC this year, probably because it wasn't ready in time for the show. But the company is definitely working on the successor to the Z3 and these alleged leaked images of the Z4 metal frame could be the proof of that.

The images compare the metal frames of the Z3 and Z4 with the similar Sony OmniBalance design. The Z4 frame is said to be 1mm thinner, however.

Another change is that while the Z3 had a flap covering the microUSB port on the side, the Z4 has an open port like on the Xperia M4 Aqua. The Z4 also does away with the dock port on the side.

Other than that, there aren't many differences between the two. We expect the rest of the changes to be under the hood, possibly with a higher resolution display and faster processor over the Z3. We will have to wait and see what Sony has in store for us.

Source 1 • Source 2

Thanks Steve and Anurag for sending this in!