...common usage is not really a justification for putting it into the language standard though. Glancing over the readme I'm not seeing anything that would require changes to the language syntax and can't be implemented in a regular 3rd-party library.
In a couple of years, another fancy technique will make the rounds and make signals look stupid, and then we are left with more legacy baggage in the language that can't be removed because of backwards compatibility (let C++ be a warning).