No, that procedure will not triger also the update of ubuntu.
sudo apt-get update - command for check the latest ubuntu packages available for your distro
But try the commands and see what will happen - nothing will be done witout your permision.
So if you wnat to be very cautious - make the backup exactly from the procedure, update your distro and then the ISPConfig's.
From my experience - i've made the update to Ubuntu without backup and nothing worse happen. (my server is virtual machine - so i took a snapshot before).