Plain text is the lingua franca for storing information that is simultaneously readable and writeable by computers and humans. It can even be converted to physical form and encoded back to digital form with no loss. Plain text file formats are unlikely to go away.
Plain text ceases to be portable when the grammar needed to parse the content is unstable. This is true in both spoken languages and computer interpretation. For example, markdown is stored in plain text, but can’t always be reliably interpreted for formatting because there are variations in the grammar.
- EBNF grammars could make plain text storage more universal