On the web, the technology that gets used the most is the technology that wins - from HTML and (in the old days) Flash to Typekit and Twitter. It's another thing entirely for him to be held to that promise because designers or developers like you hold him to it by participating in the discussion around HTML and its features. It's one thing for the editor of HTML5 to declare that the spec is designed to be practical and solve real problems. 'You can, however, join the WHAT WG or the W3C to ensure that your voice as a designer/developer is heard as the standard evolves.

On that level, then, the answer to your question is, you don't need to do a thing.