Yup, it's not that FOSS is immune to enshittification, it's that it puts power into the user's hands should that time some.

The worst case is that Godot forks, rebrands, goes private with the rebrand, and leaves the public branch unmaintained. But in that case your current game isn't screwed. It is still yours, can't be nickle and died, and you have source code access to fix any bugs (even if you lost a lot of support). Though, it is very likely someone else decides to maintain Godot as a result of this.