By targeting DEX, which happens to be documented, there is at least the hope that for the Android tooling that Google cares about, it is just like Java running and there are less hurdles.
So, you get the same benefits of the languages that target other VMs like JVM, CLR, BEAM and so on.
As long as, the language semantics can map into the VM semantics, all the libraries and platform tooling are available without the need of writing wrappers.
True, that is a big "as long as", but it still is less problematic than going through the current state of the NDK.
So what does this look like in practice? Genuinely curious :-)