That's not possible with something that is open source. If it has a "dual license" that means you can pick which license to apply. You just pick the one that doesn't make you pay.
https://opensource.stackexchange.com/questions/5599/any-succ...
You get a GPL version of the code, which is free and nobody can charge you for, ever.
If you want to use the software in a way that is not GPL compatible you can opt for the other, paid for, license.
This works in some cases, but in the case of Godot (assuming we were to do something like this) is the MIT license, which already gives you the rights to do whatever you want.
And even in the GPL case, if the other license terms became too odious you could simply switch to the GPL version, and not pay.
https://github.com/SixLabors/ImageSharp/blob/main/LICENSE#L2...
https://news.ycombinator.com/item?id=33301518
Again, nothing stops someone from forking and maintaining.
Are you saying this is not legally enforceable?
The commercial licence is just an additional option for companies willing to pay to not adhere to the GPL terms.
There are certainly cases where maintainers have started licensing _new_ versions of a project under different, non-open source terms (Terraform, ElasticSearch etc.). But you're free to continue using any code that was released under the old licence.
There are some badly written licences which make it ambiguous whether the licence can be revoked in future (e.g. Wizards of the Coast with the OGL), but I have rarely seen this raised as a concern in a software context.
(IANAL, this is not legal advice, etc.)