Ruby, Python, JavaScript, Java and others also aren't "official Google", "Apple", "Microsoft" languages and they still run the whole web. It really question the brokenness of a company processes that refuses to use good tooling just because a corpo didn't tell them to.
Kotlin is full interoperable with Java APIs and libraries and at this point there's really very few cases where it's not a significantly better choice for Android development.
That's true for now. But there's nothing stopping Google from making changes to Android which break Kotlin support in ways we could never predict. From that standpoint, Java seems much less risky if you're building a large app that you expect to have to maintain and support for years to come.
> But there's nothing stopping Google from making changes to Android which break Kotlin support
It won't, that's what they addressed in this post by ditching jack and switching back to javac bytecode.
"Over time, we realized the cost of switching to Jack was too high for our community when we considered the annotation processors, bytecode analyzers and rewriters impacted."
Now you ask, SCADE partners with PerfectlySoft is now release SCADE for beta testing, you can run Swift coding on iOS and Android (Swift or C to JNI support is in their roadmap).
http://scade.io or chat slack channel perfect.ly to chat with the team.
While Kotlin is nowhere to be seen on Android SDK and Google is officially silent on its use.
This matters a lot to customers IT departments, writing the set of delivery languages on their Requests For Proposal to consulting companies.