I think a much better way forward is proposed by Jake Zimmerman[1] of the Sorbet team. That is to allow the runtime to parse RBS inline format comments.

That retains Sorbet’s fast static checker and its runtime checks which Typescript compiled to JS lacks.

1. https://blog.jez.io/history-of-sorbet-syntax/

It should stay true to itself and not do it at all.

Sigh - all languages needn't converge into Grey Goo.