OK, what browser isn't flash support in? Yes Flash is a plug-in but Flash is on 97% of PC's. Adobe know that Flash won't live forever (on mobile devices anyway), thats why at the start of the year Adobe dropped development of Flash for mobile devices so it could concentrate on HTML5 for mobile devices. This came about because of of the Adobe vs Apple fight, and the search for better standards. Adobe have NOT dropped Flash for any other device. FYI iOS already has support for some HTML5 capabilities just like a lot of browsers.
What I meant by HTML5 not being supported in all browsers was the fact that it is still in its draft period and there are no 'standards' that all browsers are using. All the main browsers, IE7, IE8, IE9, Firefox, Chrome, Opera and Safari have SOME HTML5 capabilities however not ALL.
You're comment regarding 'People need to update' needs to be back tracked. It is very hard for developers to cater for everyone, for christ sakes we will have to cater for the moron's that are using IE7! Building a website that works in IE7 and that has HTML5 capabilities isn't as easy as just 'updating'. I go back to what I said before about HTML5 not being a standard yet either, its still a draft. Just like CSS3, but thats a whole other pot of worms.