We understand that even those that unlocked the bootloader prior to this update, without backing up their TA partition, will be able to resume camera functionality with the latest 14.2.A.0.290 update. Sony’s bootloader website has not been updated to reflect this news, but we have reached out to Sony to confirm this news and will report back as soon as we hear more.
Update: Sony has now officially confirmed that this bootloader issue has indeed been fixed.
The official bootloader website has also been updated and comes with the following message:
To unlock the Xperia™ Z1 boot loader, you must update your device to the latest software (build 14.2.A.0.290, Android 4.3). Unlocking the boot loader on earlier software versions will stop the camera functionality.