Async won't be happening in the foreseeable future for a magnitude of reasons.
It won't be easy to handle, I've made a quick test as you mentioned however i don't think it actually EXECUTES the function async, just calls it async whilst the rest is ran on the main thread, I also see no reason to recreate something that skript-reflect does so flawlessly:D I also don't want to create issues if it is wrongly done. Also i don't want to have your average joe saying "oh async! async fast! everything async!" and having to deal with that.
Yeah that's about it, other than that skjade hot x