I suspect that we'll be seeing ObjC for a long time, as the lower-level system language for Apple devices. I know that Apple still uses it for much of their system programming. No idea if that's by choice, or legacy (possibly both).
I was looking at the upcoming async/await stuff for Swift, and it's still not comparable to some of the lower-level threading systems.
That said, I have not done system programming for a long time (unless you count drivers). I think Swift is an almost ideal application-level language.
I'm not especially bothered by it being Apple-only. It works on all Apple-supported hardware, has a new application toolkit coming into play (SwiftUI), and has a very active development community. Spend some time on the Swift discussion forum to see some pretty heady discussions.