await is coming, maybe even in C++ 17. Visual Studio already implements it. Way more efficient than the C# implementation too (coroutines)
Promises are already there.
Promises are already there.
This will also only be fixed in C++17. Boost future already implements more of this, but afaik it's still flagged as experimental, so it could change again. And afaik there were also some pending discussions about how futures should interact with schedulers/executors.