Steve Troughton-Smith, Michael Lauer, Dan Leivers, Peter Molnar, Todd Thomas, Ian McDowell, Simon Wolf, Marco Arment all didn't seem (2017-10-04) in a particular hurry to adopt Swift. 
The following quote from Steve Troughton-Smith in the article that I linked was enough for me - I'm not going to beta test Swift for Apple either.
>I'm not yet convinced of Apple's level of participation in the language — four years on, Swift is not used for important pieces of iOS, OS or frameworks (I maintain a running list of Swift apps from Apple on Twitter, and macOS is definitely less shy about adopting it for new features than iOS). I understand why that is the case (ABI stability, etc), but if Apple's not using it for everything I don't see why I need to be beta-testing on their behalf. I lose nothing from waiting until Swift is 'ready', and I gain all the benefits of Objective-C in the meantime.
$ otool -L `which launchd`
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1252.50.4)
/usr/lib/libobjc.A.dylib (compatibility version 1.0.0, current version 228.0.0)
/usr/lib/libauditd.0.dylib (compatibility version 1.0.0, current version 1.0.0)
/usr/lib/libbsm.0.dylib (compatibility version 1.0.0, current version 1.0.0)
/usr/lib/libdz.dylib (compatibility version 1.0.0, current version 110.50.29)
I guess we can go through the videos to track down where it was communicated.