This is the Sony Xperia X Compact42
Right now, there are absolutely no details on the features of the Xperia X Compact, but we can see the front of the phone - on the left - thanks to an image revealed by Evan Blass (@evleaks) on Twitter.
Assuming it's going to be released soon, the Xperia X Compact will become Sony's fourth Compact handset, after the Z1 Compact, Z3 Compact, and Z5 Compact. Both the Z3 Compact and Z5 Compact have 4.6-inch 720p screens, great battery life, and powerful processors. The Xperia X Compact will likely have a lot in common with these phones, offering top-notch features in a small package. Would you be interested in such a device, now when almost everyone seems to prefer large screens?
source: Evan Blass (Twitter)