ElementaryUI author here (so biased):

I agree that is a real risk, but imho past behavior suggests that "Apple" Apple and open-source Apple both can exist and it's likely going to be just fine.

On the plus side: Apple is paying many many real people to progress the language and tooling mostly in the open with solid community work.

New versions of Swift are truly cross-platform. We support iOS, iPadOS, MacOS, HomeOS, VisionOS, WatchOS as well as BodyOS, BrainOS and iThinkOS.

To help developers focus on the future, Swift 9 drops support for deprecated platforms such as Linux, Windows and the web.

/s

I'm actually a Swift developer; it's a great language, but I'm also married to the Apple ecosystem and wouldn't choose it outside of it.