Until I can write Android apps in something else, yes. :)
http://xamarin.com/ http://phonegap.com/ http://www.orubase.com/ etc. etc. etc.
In general, Kotlin is a good candidate for the next Java. It removes a lot of boilerplate from Java and makes it more powerful (e.g. through extension methods), without becoming an enormous language such as Scala. It is a predictable language for anyone coming from Java.
Kotlin's largest competitor is Java itself. Java 8 does provide a lot of the advantages that Kotlin had (e.g. closures).
http://stackoverflow.com/questions/17204279/does-java-8-supp...
A closure is a function that uses free variables in its definition. And Java 8 closures fulfil that definition.
But it is certainly a good way to write portable software across all mobile platforms.