Hey,
I'd say the hardest part is behind us now with the release of Brotato!
It was technically challenging but all good in the end - we're doing the same work right now for Godot 4 games, hopefully ready by this summer.
Now going forward, porting a Godot 3 game will be easier for sure, but not 100% automatic : every project has its own difficulties / particularities that would need some adaptation/retake on our side. But definitely easier than one year ago 🙂