schlamar: There are plenty of places on the internet to be uncivil, but this forum is not one of them. If you feel the need to prefix something with "I don't mean to be rude" or similar, then just don't say it at all.
If a plugin wants to use futures, a plugin can use futures. S3 is fundamentally the same as S2 here, it relies on plugin authors putting in the (large) effort to ensure their plugin doesn't do any significant work on the main thread. The async events provide one way to do this, and the threadsafe API is another way that S3 makes things simpler for plugin authors. Neither has to be used, they're simply options that people have. Both of these could be done in S2, via threads and set_timeout, respectively, but the S3 approach makes things a little easier for plugin authors. Saying 'use futures', in and of itself, would not.