Currently updates are only available for online installers.

Qt users would be interested in feature to update installations done via offline installer.
Here is one description of wanted features from a user:
"
*
create an installer that can act as updater also,
*
So, if the installer starts and recognize the application is already installed,
should switch to updater,
*
our target PC usually have NO internet connection, so I cannot use online repository
*
the updater should override only target files and should take configuration files as they was
before updating,
"