Although Tails heavily depends on microformats right now, I never really saw it as being an extension just for dealing with microformats. That’s why I chose the name Tails as oppose to My Big Ole’ Honkin’ Microformats extension. Tails is about viewing and dealing with embedding data on web pages, and microformats is currently the best way to do that on the web. When embedded XML w/ CSS catches, Tails will support that too.
Having said that, I don’t see microformats going away very shortly, at least not because of embedded XML. Creating microformatted content is hard enough - I can’t imagine a lot of content writers and/or web designer buying into this over-engineered approach and having to worry about multiple XML schemas, namespaces, and properly formatted XML when creating their web content, even in the presence of tools that will purportedly make this easy. This stictness/wellformed-ness is too counterculture to the web to be massively adopted.