There is an interesting interview with the X/HTML 5 team overhere.
The things I'm most hoping for will end up in the final spec are the improved input elements and the datagrid, but that might be because for those two I can most clearly envision how they will improve my work as a webdeveloper (less client side scripting needed, hurray!). It would not surprise me that in the end the things that mean less to me now will change the web most, like the vague activex component some company from Redmond introduced for their Outlook webclient, which now is the foundation to AJAX.