Why is Swift important for the Apple ecosystem?
As the platform evolves, the way we develop for it also needs to evolve.
Since the beginning, I've seen many developers comment that developing for iOS is very difficult, highly complex, and that they wouldn't have time to learn how to develop.
With Swift, this scenario will change. I'll try to mention some of the interesting points below, both for developers, iOS and OSX users, and also for Apple, which is the most interested in this change.
Please note that it's still not possible to publish apps in the store using Swift. It will only be possible using the iOS 8 SDK, which will be released by the end of the year, most likely.
To Developers
Part of the apprehension in developing for iOS arises from the fact that the language used to be Objective-C, where manual memory management was required before the introduction of ARC. This frightened many developers because nowadays, most languages don't require this type of control.
New Developers
In addition to Swift being much simpler and safer by default, it is also much easier to learn and teach. Now, developers have access to the Playground. The Playground is a part of Xcode where developers can run sections of code and easily see the results happening, including the interface and performance metrics.
In other words, this makes it easier to teach iOS development (not to mention self-learners).
Development Speed
Swift allows for faster app development for various reasons: less complexity in dealing with memory issues, cleaner code, and the language provides many development conveniences, things that were not possible with Objective-C.
For Users
In the end, the result ends up in the hands of users (literally).
With all these changes and the influx of more developers into the market, more businesses and applications will certainly be created. Although there are already many apps in the store today, there is still a lot of room for new businesses, especially those that make a difference in users' lives.
Apple
With the increase in developers and businesses being generated, more people will buy Apple products, whether they are new developers or new users.
In the latest WWDC, Apple made it clear that it is a hardware company. Now, with iOS and OSX integrated, everything will run smoother, and using Apple's platforms will bring significant benefits to the user. Some very interesting articles describe these functionalities for those who want to learn more.
I believe Swift only adds value to Apple's platforms and has a bright future!