Yes, however some features in TypeScript are only supported when targeting ES6 (such as "const"), so there's still some value in double-transpiling from TypeScript -> ES6 -> ES5 (I'm doing that on a couple of projects).

That may have changed somewhat in the TS 1.5 alpha - they're supporting more features on the ES5 target than they did in 1.4.

But yes, you still can't use ES6 features that TS doesn't know about.