There's an interesting pattern developing (hopefully). Things that used to be GUI-only are now getting text interfaces, many times with some modified version of markdown. I made a free tool to capture analysis notes and diagrams a while back. You can see a demo here: https://www.youtube.com/watch?v=tFVfTpXCIiI As part of that, at the lowest level of detail I wanted a way to capture diagrams using plain text. Something universal.
We're almost there -- not quite there, but close. I found ways to do Activity Diagrams, flowcharts, domain models, and some other stuff using text. The formats were just a bit too dissimilar for comfort.
Why use text for all sorts of things that used to be graphical? Version control, text slicing and dicing, separation of document from view.
I'd love to see this trend continue, along with a consolidation into a super-markdown syntax. It could handle calendaring, diagramming, perhaps even layout -- along with what it currently does. I don't think you'd have to hack it up too much, but admittedly I haven't looked into the spec that much.