It's already happened for 3d modelling (Blender) and digital painting (Krita), and it feels like gamedev is an even better market for this to happen in than those because all the users are also going to be capable of contributing to development of the engine.
From the outside Godot looks like it's the closest to ready for building proper AAA quality 3d games.
I've also actually used Bevy and if you're a fan of rust and ECS based development it's really nice for building procedurally generated stuff that doesn't need a level editor, or for building 2d games and relying on a 3rd party editor like Tiled or LDtk. However there's plenty of places where it's still a bit rough around the edges, like dealing with more complex multi stage asset loading pipelines.