Things that are closely related: ebooks, the CMX and Cocktail music packaging formats, the offline features of HTML 5, and single page web apps. And maybe Adobe AIR.
Except that epub, the open format of ebooks, usually doesn’t support Javascript.
If I had to bet, I’d put my money on epub. The model of providing a zip file of HTML with an XML manifest is an easy evolutionary step which has been invented independently many times. CMX/Cocktail could easily migrate in that direction.
Epub uses an XML manifest, not something developed under the microformats.org umbrella. My experience with the XML is that it’s a bit cumbersome and could be simplified by using more plain old semantic HTML in its place. But whether a microformat.org production is more useful than plain old XML is a different question.