You saw that right! There’s a revision of EPUB 3 in the works. It’s still a working document, but makes for fascinating reading. Among the changes:
- Metadata: only title, identifier, creator, publisher, and type will be allowed in the .opf. The Refines elements is dropped, with a file-as attribute added.
- The toc.ncx will not be supported. That’s a legacy EPUB2 navigation file, used only by Nook at the moment.
- Similarly, the guide element is gone from the content.opf
Read it all here: http://www.idpf.org/epub/31/spec/epub-changes.html