The ecosystem is far more important than the language. Swift has a chance to rival Java in adoption.
Do you realize how far Java reaches into the enterprise?
And with Swift's focus still being around the walled garden of iOS/OSX development, even with the open sourcing there are many more "IFs" to achieve before Swift rivals Java in adoption.
Don't get me wrong. I don't use Java and I have made apps for iOS (though not with Swift yet unfortunately). I like Swift and intend on trying it. But rivaling Java? Certainly no time soon.
Swift is only one1 but with open source and cross-platform ability (Microsoft will port to Windows), I think we have several million Swift developers with 5 years.
[Update] 30 -> 20
20.