HTML won't be replaced as a standard any time soon. It's too wide spread a technology, and the amount of re-education required among people working with webapps and websites to switch technology completely would be massive and very costly.
HTML will however, like any other technology, evolve. Look at HTML today compared to 10 years ago, it's the same language in the basics but the way we use it, and add-on technologies have changed it quite a lot. Even a high tech, premium site made 10 years ago will look feeble with todays standards.
So, while HTML will like stay "the same" (i.e. follow the natural evolution of a standard), the technology behind the site (php, .NET, JAVA etc.) will probably be more likely to change.