This answer won't stand the test of time, but as of today:
- Objective-C will be around and supported for a long time. (Apple has a massive amount of Objective-C source code that it's not going to port to Swift any time soon.)
- Almost all iOS tutorials, examples, and books use Objective-C.
- Almost all iOS-specific third-party source code you might want to use is implemented in Objective-C.
- It's easier to use C and C++ libraries from Objective-C than from Swift.
- There are many Objective-C experts you can get help from. There are very few Swift experts.
- The Swift language and its standard library are currently not very well documented.
Stick with Objective-C for now. When you're comfortable with the iOS SDK and Swift is better documented, you can consider learning Swift.
UPDATE
It's been four months and my opinion on this hasn't changed. If you're looking for a more recent answer, this Hacker News thread was asked and answered today: Is Swift ready for production?
