There's not really a gap between them. I've spoken to people on the TypeScript team a number of times. Jonathan Turner and I talked about sharing ASTs once, and

There's not really a gap between them. I've spoken to people on the TypeScript team a number of times. Jonathan Turner and I talked about sharing ASTs once, and I gave an internal presentation about Babel at Microsoft last year. Also, there's tons of people that use TypeScript for type-checking and stripping types and then use Babel for compiling down ES2015 code since Babel follows the spec closer.