HTML5 sure has a lot going for it, given that Google, Microsoft and Apple agree to the direction it is taking. A short tour of the key features of HTML5 should be enough to convince ourselves that support for greater interactivity is getting entrenched in the browser.
Many features currently provided by large JavaScript libraries such as JQuery will be native to HTML5-enabled browsers, slimming down libraries considerably. Laborious validations will move into the browser. New HTML5 APIs allow drag-and-drop. Video is embedded easily without the need of JavaScript - although codec compatibilities are yet to be straightened out for all browsers.
There is some discussion about how HTML5 impacts the future of Flash. To me, the larger issue is how it impacts the future of the Web. The very prospect of better interactive support in browsers is a positive sign for the future of the Web. Interactive applications will be easier to build and deploy - and users will find the Web content more engaging.