[dleslie]

Unless Godot has solved the problem of forward compatibility of binary asset bundles with compiled assets, then what's true of Unity is true of Godot: the cost of your engine upgrade is proportional to your reliance on existing assets.

It may just be a recompile. It's may be that the upgrade requires more, a whole art pass before recompile. Maybe there's mods you don't have the source for, that you can't upgrade at all.