On the contrary. If the application of HTML doesn't take advantage of growths and changes made by the w3c, then the language has outlived its usefulness, and I fear that the corporate requirement of marketing has made that so.
Professionals always have to worry about having the page look good in older browsers.
Thus, the solution is to devise a new language that won't even be read in older browsers, period. Progress needs to be made. The beauty of XML is that it has the potential to allow growth and change, while still being compatible with xml 1.0 browsers, through the ability to create new dtd's and schemas, and the XML namespace. THAT is the flaw of HTML that XML fixes, and arguing over the case of tags is ridiculous. It's a step backward for us in terms of professionality.