I often wonder what things would be like if Apple had improved upon Objective-C by fixing up the underyling C language. Yeah it'd no longer be a superset of C, but so what? Neither is Swift. Swift is great but I wish it was closer to Objective-C in spirit by deliberately being a more lightweight language. It's language spec is gargantuan - they've pretty much succeeded in making it a language as complex as C++.
Merely adding generics and better typing akin to TypeScript's, to Objective-C would've worked wonders and made the transition less abrupt.
https://medium.com/ios-os-x-development/generics-in-objectiv...
I still rely on some stuff like GCD that isn't very swift like, there still isn't anything as fine grained in Swift, but I'm liking combine in some cases.
For professional *OS development Swift probably makes sense. But if I occasionally need to write some code, Objective C for me is preferred. May be Swift is stabilized enough already...
The biggest source-breaking change on the near-term horizon (which is still in progress) is compile-time enforcement of concurrency safety.