Objective-C and Swift. The two programming languages that are hitting the Apple developer’s community right now. It’s like a choice of your company to select one of these languages or choose both of them giving priority to the developer’s choice.
The best thought to consider is, Apple wouldn’t be interested for a full fledged investment in Swift, if their ultimate goal was to replace Objective - C. Apple isn't yet ready to declare that either.
Swift is a king for early adopters of this language. And for others it’s like sticking to the old school level they are mastered in, Objective-C. But today, it’s hard to become a Swift developer without first being an Objective-C developer.
Swift has it’s touch towards Python 3 debacle. After few years of Python’s release most developers write code in 2.x. There is a problem with backward compatibility too. So you cannot convince a whole community for rewriting perfectly working codes for Python 3, yes the code purity isn’t enough for Python 3.
When migration from Objective - C to Swift becomes stable, developers can have a fresh way of working with Swift. Apple can conveniently say “Developers should be using Swift” and can discourage Objective - C. But removing Objective - C is merely impossible, because it powers iOS.
For the conclusion, if Swift is here to succeed, Objective - C will fade out. It can enjoy it’s vacation at Miami keeping the legacy of many powerful apps with million of lines of code. Many years from now, when you see the pillar libraries written in Objective - C, it will be remembered.