With the release of Swift, Apple not only put on the table a new language with cool stuff, they want to change the way the developers create code, promoting the use of protocols instead of classes whenever possible.

Why to use protocols? Easy, more protocolos more flexibility and with swift Extensions  now we can implement generic behaviors delegates disengaging the code. Decoupling + flexibility  is the Holy Grail of software engineering.

Do we fully replace the OOP? Of course not, but it is the perfect complement, remember that Swift can only inherit from a class but can use any protocol you want.

If you still have doubts about trying  Swift, look at the video of Protocol Oriented Programming https://developer.apple.com/videos/wwdc/2015/?id=408 If you are a software lover you would appreciate it.