HTML 5's standard is being born and lots of things, I think, is happening in the browsers developer team. This draft is a trace of the growing up semantic web. It make the base to a new web that is beginning to appear in our browsers.
The next decade is the time to give to the web a 360º rotation. Now, we've to walk the first footsteps, someone've already walk this footsteps. I can named three companies leaders in this matter: Microsoft, Google and Mozilla.
This began one/two years ago with the first releases of Google Gear, a local database for better the web 2.0 applications (they used it for Google Reader for example, a full RSS reader online); Mozilla is developing the 3 release of their browser Firefox, whose a main feature's, between others, the local storage of Web 2.0 applications to access them offline; and Microsoft released the Silverlight 1.0 RTM release, a multibrowser and multiplataform plugin to develop Rich Internet Applications (RIA) that someone compare with Adobe Flash, some mouths ago.
These technologies have some features in common, they've the same reason: making the web more interactive.
But it has a problem: the accessibility.
For want of standards, developing a accessible browser (or make accessible one of the existed) is hard.
First, I think that the current browsers must be accessible. And second, the new technologies should be accessible too. The web developers should know the standard and use it to make his websites. And the browsers must force to use it.
For force it, the browser html parser must validate the HTML, CSS and scripts to know if this document is valid. If the document is invalid, this must shown an exception. But, I think that this imply a objection. The document can't be parser "on fly". I don't know how the browsers'll parse the XML implementation of HTML 5. I believe that the browser will only show the web page when it finished to download the page, this is logic, although the XML must be valid.
The HTML 4 shouldn't be forgotten, for example to use WYSIWYG (What You See Is What You Get) editors, like the used to write this post (Windows Live Write), due to their features they cannot edit the CSS Styles and the presentation elements should be used.
But the futures is in this draft, in the other standards and in the companies that participate in this draft and developing the technologies that are going to revolutionize the Web. I don't know if it's the web 3.0, the semantic web, the web 4.0 or the web 100. But the future are in the double life (the real and the virtual), the multimedia content and the nobody-know-what new sites will appear nobody-know-when [:)].