It's going to be Swift

In just a little over two years, Swift has become one of the software development world's most talked-about programming languages, and is even the most forked repository on GitHub (but then, how many new languages have the power of a multinational like Apple behind them?). The language has undergone (and is still undergoing) incredibly rapid evolution, guided principally by Chris Lattner and the team at Apple, but also by the wider community, since it was open-sourced in December 2015, with proposals for language changes by non-Apple developers being included in the release of version 3.0. This radical departure from Apple's usually secretive product development strategy has meant that Swift has already benefitted from the experience and perspective of a great number of developers of mixed backgrounds (in every sense), with Apple itself saying that release 3.0 contains work by a total of three hundred and sixty-odd contributors.

If you are coming to Swift from Objective C for the first time, you will find it a much more succinct and clear language, one that needs fewer lines of boilerplate code, not to mention fewer semicolons, than its predecessor. If your background is in Python, JavaScript, or Java (to name the obvious ones), you'll find the code much easier to understand at first glance than would have been the case with Objective C--this is a good time to add Apple's platforms to your portfolio.