Currently, there are no general-purpose applications that support arbitrary XLinks. That's because XLinks have a much broader base of applicability than HTML links. XLinks are not just used for hypertext connections and embedding images in documents. They can be used by any custom application that needs to establish connections between documents and parts of documents, for any reason. Thus, even when XLinks are fully implemented in browsers they may not always be blue underlined text that you click to jump to another page. They can be that, but they can also be both more and less, depending on your needs.