90% of what you learned are Cocoa frameworks and Apple-flavored OOP patterns that will be totally applicable to apps written in Swift. Fear not!

I don't know very much at all about objective C, but the way these things generally work is that you will benefit from the experience as you learn new languages, as it will be an anchor of context against which you may base fresh perceptions.

You'll always be able to contribute to NeXTSTEP. It's not dead yet!

No worries, Objective-C is faaar from deprecated.

Objective C isn’t going anywhere.

Swift is shit. I suspect it will die in a couple years, like the misguided effort to get people to adopt the Java bridge or WebScript before that.