It is a way of deliberately putting down some of the often-silly dynamism Javascript provides.
Whether it takes off or not, I can't call it a "contender to replace Javascript" when it is Javascript.
I think you meant 100% backwards compatible with ES6. As far as that goes, it sounds like a pretty good addition to the ES6 standard.
What is hard is to change JavaScript from the outside. They may have found that impossible to do. The direction started with asm.js shows that JavaScript needs to change from the inside. JavaScript can be changed and remain largely compatible, but it will not be without the drawbacks. The path started with transpiling and polyfills may help to keep some backward compatibility, for example. :-)
Not all problems can be solved with just 1 technology. It will continue to look more like a mash-up. The challenge is to make it cross-platform. Google have to run ads on those things for it to help with the bottom line.
Better tooling, better performance, why would I want to go back?
The language of the future includes a Javascript compilation target.
TypeScript (and to a lesser extent CoffeeScript) seem fine to me, but ClojureScript looks very different to JS. I'd always advise someone to learn JS first, then your compiled language of choice.
I'd also worry that the TS community itself would risk marginalization, end up as a small niche ghetto, with most of the interesting stuff going on in ES7+.
Hard to be sure but I wouldn't write off JS just yet, people have been doing it for years as new/better (flash/silverlight/compile to JS) technologies have promised to make it seem soooo 90s.
Going forward does not mean abandoning Javascript, just abandoning ES5
" 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 :-)."
You can do almost anything in JavaScript these days. The down side? You can do almost ~anything~ in JS these days. Including lots of stupid things.
Since JS works extremely well for user interaction, and is "good enough" for simple object-oriented programs, it will likely never go away in the foreseeable future in these realms. What I think things like SoundScript are for, is 1) for people who are used to strongly-typed programming languages to feel more comfortable on the web (which is actually pretty important), and 2) for larger OO or enterprise-style systems that really shouldn't have been written in JS in the first place (I'm looking at you Angular).
I wonder if it will end up like Go, though. An interesting language which never gets more than a niche market.