HTML is such an old and cumbersome language, which was intended just to markup text. Today it's very rare to see a static HTML website, or a site with only text or a very simple layout.
As a web developer I find it inconvenient to use HTML & CSS, very repetitive and cumbersome. I think that for a lot of website it could be simplified a lot.
... though HTML will be considered part of the established infrastructure (rather than an exciting new toy), there will always be new formats coming along, and it may be that a more powerful and perhaps a more consistent set of formats will eventually displace HTML.
So, more than 15 years later, HTML is still here and it's here to stay. Why?
Answers like "it's too hard to change a standard" aren't answering the question since a lot of new standards emerged since the initiation of the web. I'm also not searching for answers that suggest using tools to simplify the process or formats that anyhow depends on HTML or CSS, technologies that currently require a plugin and not even trying to become an open standards (like Flash) aren't an answer neither.
BTW, here are 2 articles written more than two years ago as food for thought, it might help with writing a better answers.
"HTML, CSS, and Web Development Practices: Past, Present, and Future" describing a very related problem, by Jens O. Meiert.
So now you can answer questions about HTML5 without even looking at the draft, which is handy, because the draft is 400+ pages long. Why is there a new tag in HTML5? Because some browser vendor (maybe the one that also owns a large video site) wanted it. Why are there so many scriptable interface elements in HTML5? Because some browser vendor (maybe the one selling phones without Flash support) wants them. Why is there no support for RDFa in HTML5? Apparently no browser vendor wanted it.
Is that the future?