[bgarbiak]

Who would still use HTML? There would be no upside at all, Flash has always had better tools.

No upside at all? Open standards, semantic code, SEO optimization, separation of presentation and content, ability to look into the source code, ability to alter the content and/or visuals by user, better printing support, userscripts, ad blocking,... Just to mention a few.

Anyway, no matter how good Flash could have become it would always be only a plug-in. A third-party injection, not an integral part of the web - and as such it always was doomed in the long term perspective. Relaying on plugins is like - excuse an over-the-top metaphor - having nitro system in a family car. It's exciting for a while, but nowhere near an experience of having a real supercar. HTML5, in it's current state, is not yet a Ferrari but it has way bigger chance to become one than Flash (or Silverlight, or anything) ever had.