Pandora's box has been opened though. Majority of the JS community seem to have adopted Babel in their workflow.
Even as I question it, I must admit it's pretty sweet to have a transpiler in the buid toolchain. It frees one from the browser/backward compatibility question, more or less, and opens up the language to be extensible - for better or worse.
For example, Babel macros ¹ is an interesting concept, using the language to extend the language during compile time.
To bring it back to the topic at hand (PgTyped, Typesafe SQL) - one thing that I'd like to see in TSC is a way to output type definitions (either inlined metadata or external JSON schema), to be consumed for run-time type checking. That would "complete the circle" for me.
TypeScript "compiler plugins" seem to be on the roadmap, or at least under consideration ². Some may see that as opening a proverbial can of worms, down a similar road to Babel. I wouldn't disagree, but it'd be so useful!