In essence you're describing epub, which is HTML, and I agree. It has great potential but nobody seems to see it as more than a cheap ebook format, and even that is underdeveloped in terms of capabilities: presentation quality and annotation are nowhere near PDF, for example.
Most of all it needs usable editors, and editors which integrate multimedia and dynamic content editing. End users can't turn to a different editor for each media and then integrate the output into the epub document, like a web developer does (e.g., for an image use Photoshop, save the jpg, copy to the proper directory, reference appropriately in the html).
Most of all it needs usable editors, and editors which integrate multimedia and dynamic content editing. End users can't turn to a different editor for each media and then integrate the output into the epub document, like a web developer does (e.g., for an image use Photoshop, save the jpg, copy to the proper directory, reference appropriately in the html).