Thanks for the excellent write up and your work on Dart. After the long hiatus, I'm excited to see the language proposals in https://github.com/dart-lang/language, but I haven't seen anything in there regarding concurrency.
I believe that we already have necessary building blocks (isolates), we just need to make concurrency via isolates efficient and ergonomic.
However it is still very early, so I don't have much else to share.
[1]: https://github.com/dart-lang/language/blob/master/working/01...