JetBrains make Android Studio in collaboration with Google. Kotlin just became a default part of IntelliJ 15, so presumably, once that is released and Android Studio is rebased, Kotlin will be supported by default.
There are some nice Android frameworks available. But right now, apparently Kotlin+Android doesn’t do incremental compilation, so build times can be very slow. Kotlin+Regular JVM does do it, so I am hopeful JetBrains will resolve the issue soon. They appear to prioritise Android support quite highly.