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.
People still write applications in Objective-C (e.g., see Transmission [1]), and the language is still maintained to support the latest OS. If anything, Apple being the largest sponsor of Objective-C would suggest that you get greater vendor lock-in out of it than Swift, since you can at least use the latter outside of Apple platforms (e.g., on a server).
Although the only framework that was developed in Objective-C after Swift got introduced was Metal, anything else is mostly maintenance and incremental improvements.
"and dropped it like a stone with little warning or ceremony"
What?! This is complete nonsense. Swift was introduced 11 (!) years ago and it was clear from day one that it was going to be the future. Every single year since the introduction there were clear messages and hints in documentation and WWDC that Swift is in and Objective-C will _eventually_ be out.
Little warning? Maybe if you kept your eyes closed the past 11 years.
And do not forget that today you can still write apps in Objective-C.
Whether or not Apple still has legacy pieces in Objective-C or still allows you to write apps in it is not the issue. The point here is that Apple shadow-dropped Swift and shifted essentially all of its development priority away from Objective-C in a matter of months.
I'm old enough to remember when Objective-C was a real and thriving (if niche) language. I remember all the buzz when automatic reference counting was the next big thing, pushed heavily by Apple and taking center stage at WWDC. And since the year Swift came out, Objective-C has joined Cobol in the category of zombie languages: the living dead with plenty of entrenced codebases but with nothing to look forward to but a continued slide into technological irrelevance.
