Really excited about this. This is another reason why Scala is an extremely valuable tool these days. With Scala JVM, Scala.js with React Native and now with Scala Native (LLVM), there'll be literally nothing you can't do well with it.
That's one of the things I like about Clojure too, i.e. that is a good tool for many jobs, in part because it runs on the JVM, the browser (ClojureScript), and can also be used to build React Native apps (http://cljsrn.org/).
Does Scala.js with React Native work well? I avoided it because I didn't want to complicate my stack or have to jump through hoops when reading the react docs. If it all works well I might make the jump to scala front & back...