To further expand on Apple's recommendation to not make Swift libraries just yet — It's also an matter of compatibility. You could certainly make a Swift framework, but given that Swift as a language is changing every 6 months or so right now, it doesn't make sense to make a framework using Swift.

You could easily hold up another project if you haven't changed your Swift code to the latest, or the opposite is true as well: Your Swift framework is up-to-date with the latest language, but the app using your framework is not, etc.