Considering that a leaked version of the update has already been spread, it means that we shouldn't be that far away from an official release of the update for Sony Xperia Z owners. The phone came to market with Android 4.1.2 pre-installed.
The tone for the Sony Xperia Z was set early in the year at CES 2013 where it was one of the best received smartphones at the show. Sony even arranged to have it dunked constantly to show off the water resistant feature of the model.
source: YouTube (1), (2) via AndroidAuthority