In addition to various smaller Xperia handsets, this 10.1-inch tablet that arrived back in 2015 with Android 5.0 Lollipop on board is on its way to Nougat. The new software has just been spotted receiving its certification from wireless device certification forum PTCRB.
http://www.notebookcheck.net/Sony-Xperia-Z4-tablet-to-get-Android-Nougat-update-soon.191498.0.html