XML is a very exciting web development. It will enable data exchange in applications that otherwise would be stifled. For example, in HTML chemical diagrams need to be inserted as a gif or jpeg graphic. This means that the user would have to reconstruct the formula from the graphic by hand. With ChemML though, it is the formula itself which provides the means to display the diagram and so the recipient has both diagram and formula.
Does this mean the end of HTML? I believe the answer is 'no', at least for the foreseable future. XML has many benefits, but for producing simple web pages most users are going to go for something simple - HTML. This may change in the future as XML is totally embraced, but Pfaffenberger believes that HTML 'will continue to provide the baseline for users publishing; XML will be employed to add functionality.'[1]
XML has already achieved recommendation status from W3C. Microsofts' IE5 and Office 2000 both support XML implementations. XSL is still in working draft form but should soon become a recommendation. Once this occurs it is likely that other browsers and users will more fully embrace XML and its true potential can be unleashed.