I feel like everything is eventually going to go full circle back to Google Web Toolkit[0]. The original "write it all in X language" toolkit with compile to JavaScript functionality.
I was a massive GWT fan - particularly because it played well with the Java ecosystem.
1. huge programmer pool
2. tried and tested legacy code could be easily used / adapted
3. code quality / checkstyle plugins just worked
4. great testing tools
My main gripe was the compile time (often 2-3 mins)...whereas Adobe Flex would crank code out in 3 seconds.
Now, the new language models should help us push through the noise.
[0]: https://www.gwtproject.org/overview.html