Flash revolutionized the internet, no doubt about it. It made things interactive back when javascript meant some annoying, lagging snowing-effect on webpages. However, Flash is definately falling behind, I see it used mainly for 3 things: games, video-players, and ads. I don't think us consumers give a rats ass about ads, so that just leaves video and games. Since HTML5 can handle both those things, is open, and doesn't require unnecessary plugins (video codecs aside), it only natural that the web will progress in that direction.
Remember when viewing videos meant installing RealPlayer or QuickTime (or worse, some website's custom spyware)? Now its all flash, and soon, it will all be HTML5. Flash will remain in the games market for some time (I don't think you can just "port" flash to HTML5), but the open HTML5 is simply a better solution to the closed Flash technology.
Think about this, Adobe Flash does NOT support Internet Explorer 64-bit version (which is really annoying because when applications request IE specifically on Win 7 64-bit, it seems to default to the 64-bit sans-flash version). The bit-depth of the web browser should have nothing to do with the content displayed. That's sort of the opposite purpose of the internet.