Comment by masklinn

ABI stability is absolutely (also) about size though, one of the big issues iOS developers have/had with Swift is/was that it would make the size of the bundle explode (compared to an equivalent objective-c application) as the application would need to bring along much of the standard library.

Until there starts being core swift-only APIs, your point is already solved because regardless of the Swift library the underlying functionality and OS interaction is mediated through a C library which is dynamically linked.