The main advantage for using "or later" is not really to be OK when a new version of the license is published, as this happens rarely.

What you gain is the possibility of combining this code with any other code that is under a later version of the license. If there is code X under GPL-2.0-only and code Y under GPL-3.0-only, these cannot be combined, since each license declares that any derivative work has to be under the same license. If code X were under GPL-2.0-or-later, the combination would be compliant.