https://www.techradar.com/news/mobile-computing/tablets/sony-xperia-z6-tablet-what-we-want-to-see-1313381

Update: Mention of two Sony tablets has been found in an official APK, but another source claims that they've both been cancelled.

Sony released the Xperia Z5 at the tail end of 2015, but its last slate was the Xperia Z4 Tablet a whole generation earlier, and more recently Sony has shown little interest in either tablets or the Xperia Z range, with the likes of the Xperia XZ2 and Xperia XZ2 Compact launching instead.