Human-readable forms of data, and self-describing data, will outlive all other forms of data and the applications that created them. Period. As long as the data survives, you will have a chance to be able to use it—potentially long after the original application that wrote it is defunct. You can parse such a file with only partial knowledge of its format; with most binary files, you must know all the details of the entire format in order to parse it successfully.
I'm more convinced about self describing atomic pieces of data. We need stronger primitives than plaintext can afford but we cant divorce interpretation and content. A composble protocol of some sort is necessary.
