I strongly believe Swift is the future of iOS development. It’s only a matter of when, and the blocker is the breakneck speed it evolves. For smaller apps, Swift is good enough. For big apps, it’s at least a year away.
If you’re working in a smaller app, stop reading. The benefits of Swift 3.0 probably outweigh the risks. If you’re curious about the challenges of large companies, large codebases, and complex dependencies, this post should explain why big projects are holding back.
We're in the run-up to WWDC, and in the wake of this announcement from Chris Lattner a week ago, that certain features slated for the upcoming Swift 3.0 have been postponed, I expect to see a ton of pieces on Swift and dynamic programming.
Sandofsky's article is a great overview of why it might not be practical — arguments over dynamism aside — for big apps to move to Swift yet.