It really depends on whether the permission set structure was altered for a particular form, table, function, or other permission controlled attribute. If things are added in, it is possible that the IFS update will reset that portion of the structure to the new structure schema in order to ensure all elements are pulled in to the permissions area. This means at times it can be necessary to regrant permissions that were already granted for certain functions or forms or whatever.
There is no guarantee from IFS that the permissions WON’T change, rather there is an indication it is possible. The Update notes are supposed to give an indication when this occurs, but in my experience they are terrible for that level of detail and the only possible method is thorough testing in a DEV environment before making the update live in the PRODuction environment.
Thank you very much for your answer. It is really helpful.