We are currently working on the guide @emmanuel_brochu, we don't currently have an estimation of when it will be ready. Please note that the process is not easy. For the moment you can follow the migration guide, which is very easy to do: https://doc.owncloud.org/server/9.0/admin_manual/maintenance/migrating.html
To migrate your installation, you should launch or install a new Bitnami ownCloud stack in your computer/instance, and migrate the data from the old instance (the current one which you wanted to upgrade) to the new one.
Note that you should stop the servers (Apache, MySQL and PHP/FPM) after installing the new installation, so you end up using the same ports as the previous one.
Let us know if you have any question about the procedure.