Apple has made it clear their development future lies in Swift, not Objective-C.
That means you're choosing between a popular, well supported language and a dead end.
The choice should be obvious.
They've done no such thing. The biggest writer and maintainer of Obj-C code is Apple. They're sitting on a huge source base they'll continue developing on. Please link me to where Apple has said Swift is replacing Obj-C. Because they haven't. And they've said the opposite many times. Everything I've read/heard is that Obj-C will continue to be a first class language on iOS and Mac (with Swift and Obj-C both being considered first class languages.) You can have more than one language on a single platform. Shocking, I know.
Not to mention, for such a dead end, Apple's still writing a lot of new Obj-C. The iWatch OS (what runs on the watch itself) is Obj-C. Apple has not shipped a single API on Mac or iOS written in Swift. Not one. So it makes zero sense that Apple would consider Obj-C a dead language, and yet continue to write source they'll have to maintain for years in it. And if you think Apple is going to rewrite the millions of lines of Obj-C in Mac OS X and iOS in Swift, you really don't understand software engineering very well.
Another problem is that Swift is missing basic language features. Obj-C can link to C++ code. Swift? Nope. That alone means Swift can't replace Obj-C code. Everyone has C++ code they need to link to. Apple has C++ they need to link to in their own APIs. So does Adobe. Microsoft. And they'll probably fix it in the future. But you can't even approach suggesting Swift is going to replace Obj-C with a straight face until that is fixed.
Now look, I'm not trying to argue against Swift here. It's a valuable language to use and learn. This isn't a desperate "Obj-C forever!" post. But if you think Obj-C is going anywhere in the next decade or two... It can't. Apple will continue upgrading it, and continue supporting it, or else they're going to end up putting themselves in a corner where they can't even maintain their own software. That's not opinion, that's realism. It's knowing when a tool is right for a problem. And we're nowhere near Swift even being able to entirely replace Obj-C in usage.
Heck, the last Xcode beta even shipped with some upgrades to Obj-C. So I don't even need to argue that point. It's not a question of if Apple will keep advancing Obj-C. They are.