Android devs already have Kotlin at their disposal - which, by the way, happens to be uncannily similar to Swift, syntactically at least.
It already has a small but loyal following, it offers 100% Java interoperability, it's backed up by JetBrains, so it's seamlessly supported by IntelliJ Idea / Android Studio, it's been highly regarded by quite a few influential figures in Android development world. And it's not controlled by Google's most serious competitor (in mobile, of course); open-source or not, this could be a liability.
And at any rate, as far as I can tell, Google adopting Swift is merely a rumour at this point.
For reasons given above, I'd rather see Google give an official blessing to Kotlin.