" Indeed we had structural types in ES4 toward the end, and almost bluffed MS into folding (I'm told by a reliable source). But ES4 was trying for too much too soon. At this point we really need to see ES6/7 and TypeScript + Flow "gene- culture co-evolution". As I said at the last TC39 meeting on the topic, big de-facto standard wins trump rushed de-jure standards any day. /be"
and also:
" Type system implementors and the JS stewards must communicate well for this to win. It's looking good so far, on Ecma TC39: JQuery, Facebook, Netflix, PayPal (Ebay originally, and again), Twitter all represented along with Apple, Google, Microsoft, and Mozilla. Also academic researchers from various universities, all of whom love type systems and theory :-)."