One of the things that I have been pushing for a while is the idea that presentation and content should be separated from one another as best as possible. This has honestly soured me on any form of XML for human-readable document unless it has a very clear set of implementations.
This all gets hazy when I discuss archive formats (which, by necessity, have to handle ugly, nasty binary data like JPEGs) but a solidly specified archive format with few interpretations is important.
I really like just regular old GitHub flavored markdown though. I doubt ZIP files are going anywhere anytime soon, put your markdown and images in there.
And the open document stuff is all standardized and probably not going away either.
This all gets hazy when I discuss archive formats (which, by necessity, have to handle ugly, nasty binary data like JPEGs) but a solidly specified archive format with few interpretations is important.