However Sony has now confirmed the obvious - the Xperia Z will get updated to 4.2 Jelly Bean and moreover it’d be the first Sony device to get the update.
"Xperia Z launches on JB 4.1, but will receive 4.2 shortly after launch. As always, we’ll share more info on this over the coming weeks on the blog," a Sony rep confirmed in a recent Q&A session.
The jump from 4.1 to 4.2 is mostly about user interface improvements but no major under the hood changes. Still, it does bring features like a new and convenient camera interface, lockscreen widgets and more.
source: Sony via Android Central