I am surprised that EDN is not making more progress as a data interchange format, especially now that it has fantastic validators and coercion libraries, such as Prismatic's Schema:

https://github.com/prismatic/schema

This is, by far, the most intelligent data exchange system I have ever seen. It offers a richer language of types than what is offered by JSON, it is as readable as YAML, it is far more concise than XML. And yet it seems unable to break out of the world of Clojure. But it deserves to be taken seriously as a data interchange language.