That "yield" keyword that Python 3.3 just added? Guess what mainstream language they got the idea from? The lambda syntax ECMAScript 6, C++11, and CoffeeScript use? Guess where that came from? Hint: NOT Java, Python, Ruby, PHP, Perl, or other open-source language of your choice.
Just wait a few years and watch at how many languages add an "async/await" feature.