Yeah... I'm pretty certain the only code in iOS 9 that is written in Swift is the Calculator app, which was also the first app I remember Apple shipping that actually used their public version of UIKit; until iOS 4, when Apple dogfooding their library finally made UIKit "good", Apple was still using the as-yet-much-better private UIKit they had written for iOS 1 that shared very little... it even had its own UIScrollView called UIScroller and its own UITableView called UITable. While I'm sure the language keeps getting better as people provide feedback, the product isn't going to move past that "omg this is amazing" threshold until Apple dogfoods it, and until then Apple is just using everyone as guinea pigs ;P.

FWIW, I think Apple can't ship any base libraries that uses Swift until they finish ABI-compatibility, as they need to be working off the same base Swift runtime as the apps that would run against those libraries. Given that for the last year people have been shipping apps that link against an old-and-incompatible Swift runtime that Xcode bundles into your app, and given how the runtime is "intrusive" (putting stuff into the global Objective-C namespace, for example), it isn't even clear yet (so this may require more time on their end to build out more infrastructure) how they will be able to pull that off without saying "all Swift apps developed before now need to be reshipped or they will stop working on iOS 10".