It was a relief during the summer when we saw most Sony Xperia devices being able to get root with locked bootloaders. This was thanks to various exploits (such as TowelRoot) that were discovered and tweaked by the fantastic developer community at XDA and other places. These exploits have been patched in the latest Xperia firmware builds, which means there is currently no method to root any Xperia Z3 series device that has a locked bootloader.
There will always be a strong demand to gain root for any handset, so the XDA community has gathered together and is currently running a bounty for whoever can root the Xperia Z3 series with a locked bootloader. The pot currently stands at $2,394 at the time of posting, which highlights the demand for Root. Hopefully it is a matter of time before an exploit is discovered, we’ll keep you posted if there is any success on this front.