Brendan Eich made the following comment here recently:
" 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 :-)."
Going forward does not mean abandoning Javascript, just abandoning ES5