Even if sum types were introduced, it would not help with nil values because - as you said - backward compatibility won't be broken.

If I had the luxury of spare time to contribute, I would probably spend it switching away to another richer language instead, because it would be cheaper, solve more of my problems and with a higher degree of certainty. And that's not even mentioning the attitude and toxicity of the community compared to most of other languages facing critics and ideas.