I haven't studied Objective-C yet, except some basics. I like backward compatibility, so I would like my iOS app work for example with iPod Touch 3rd Gen. (iOS 5) and the new iPhone 6 (iOS 8) also. In that case do I need to use Swift yet?
Edit: My idea at the moment is to make cheap apps for iOS, Android and Windows Phone for developing countries and others as well. That is why I'm interested in backward compatibility (not Swift development), because there are people who buy used devices and still might be able to buy apps to those devices. When I asked this question I was uncertain how far back I can go with iOS versions.