BTW what is exactly that Flash can do that HTML 5 can't? Annoy people, crash browsers?
HTML5 doesn't have an application like Flash CS4 to create content without ever typing a single line of code, for example, making it easier to use for artists and people who don't want to code, but instead want to create stuff.
Animating with Flash is the easiest thing to do, you can do timeline-based animation, frame-by-frame animation and tweens without ever touching the Actions panel. And it's all vector based. How do you to that with HTML5? How do you make an animated cartoon easily with HTML5 today?
And Flash has never crashed any of my PCs, it has only crashed my Mac. So I wouldn't blame Flash for that!
Videos and websites that require coding and databases, on the other hand, are not ideal for Flash, but until now, there was no alternative for years. HTML5 will probably do a good job at replacing all that, but slowly, since I'm sure not everyone wants to pay for a new website right now.
At the moment there is nothing Flash can't do that HTML5 can do, only Flash does some things much less effectively if you have an old computer.