We've heard several times that Sony is changing the design of its handsets, and in the case of the Sony Xperia XZ2 Compact that could mean a curvy, likely metal back.
You can see it in the image below next to a Sony Xperia Z5 Compact and it's clearly a lot less angular than its predecessor, though may also be slightly chunkier.
Not quite final
Apparently this is a prototype, so may not be totally identical to the retail handset. For one thing, the final version is said to have a slightly smaller bezel above the screen, but this may not be far from the launch version of the Xperia XZ2 Compact, though as always, we'd take it with a pinch of salt.
Given that the Sony Xperia XZ1 Compact was only announced in August we might not see the XZ2 Compact in any official capacity for a while.
However, given this image has leaked, the fact that Sony doesn't always wait a year to refresh its phones, and that the standard Xperia XZ2 is rumored to be coming soon, there's a chance we'll also see the new Compact very soon.
- The Sony Xperia XZ2 Compact could land at MWC 2018