Yes, but it isn't enough information and TBH i do not think that at the language level you can have something that will provide a good enough UX (but then again i'm not in favor of Javadoc-style comments and i believe documentation should lie outside of the source code).

As far as I’m aware (caveat: my knowledge may be slightly out of date here), none of the older .NET async patterns - APM, event based async - have been marked obsolete despite the task based versions being preferable for a long time.