Apple was the primary and only major sponsor of Objective-C, used it as the core foundation of their entire platform, and dropped it like a stone with little warning or ceremony. Yes, being tied so closely to Apple is an existential risk for Swift. One need only look at the quality and trajectory of MacOS to see that Apple isn't a software company, let alone a company that cares about developer experience (Xcode, anyone?). As far as modern Apple is concerned, the primary benefit of Swift is that it produces a tiny bit extra lock-in for iOS apps, by making cross-platform development more difficult.

Rust of all languages, now that it's been majorly adopted by many companies big and small, has a higher risk of losing support over a language developed exclusively by one corporation? I sincerely doubt that.