I will love to see how Android apps will be written in Swift, not because its an Apple language, just because I didn't like Java at all (don't know the Oracle Java but the Java supported by Android lack of some features of an actual language).

Also the first challenge will be to build a library that implement all the Swift UI elements to Android (or vice versa) or better Google reinvent their UI or at least add more features and turns Android in a real MVC (bind the view with the controller).