Wiping the <LOL> off your face
You clearly haven't even bothered to look into how web pages work beyond Flash, but here's some info anyway.
"Experience tells me that embedded font rendering is a major reason why most brands choose Flash for interactive media, because they can't use the relevant branded fonts in other solutions - it looks crap."
All the major browsers now support embedded fonts via CSS3. When people talk about using HTML5, obviously that implies the use of CSS and Javascript. Recently, the major browser companies have even agreed on a standard font format to appease font companies who need to protect their IP.
"The latest Flash Player even moves into dynamic typographical layout territory and makes use of overflow text boxes, something that you'll see in Quark Xpress, Illustrator and Indesign."
The latest Flash player uses Webkit to render all that stuff. It's practically Safari with a load of plugins and scripting libraries. So, anything Flash can do, Safari can do. And so can any other browser. Opera can rotate text and skew it and do all sorts of stuff.
"handle tween animation?"
CSS3 transformations. I use them and they look nice in Opera, Safari and Firefox.
"handle in-stream video metadata?"
To do what? HTML5 browsers have in-built players that read the meta data.
"Hardware 3D acceleration?"
Where have you been? That's the big fuss MS are making about IE9. Opera's new Vega graphics library was designed for hardware acceleration, and there are even test builds from years ago on YouTube showing it using hardware acceleration to do interesting stuff. The current version of Opera has it disabled by default, but they didn't design it to do hardware acceleration for no reason. Clearly all the major browsers are moving toward it as Web 2.0 Apps have provided the necessity for speed. The first step was speeding up Javascript, the next will be hardware acceleration.
"Real-Time text effects, e.g. glows, drop shadows etc."
Old news. CSS does these already. I've been using box and text shadows for a couple of years now.
"Easily fill a screen with content irrespective of its "design size""
But that's how HTML has always worked. It's only when someone starts specifying absolute widths that you run into problems. CSS has rules to cope with different screen sizes, aspect radios, portrait or landscape, units for setting text sizes, line heights or boxes based on the width or height of the viewport, and a whole lot more. And then there are browser features such as zooming and fit-to-width.
"Interface with external devices, e.g. webcam streams etc."
Yes? All covered by the HTML5 'devices' spec. You really do need to look into these things before preaching and LOLing from your porch rockingchair in Hicksville.
And just wait until you see what the <canvas> element does! You'll feel like a flat Earther being told the world is round!
Flash is the only viable solution to these things today. But the web moves quickly and empires fall. Mosiac, Netscape, IE, Yahoo, Perl, XHTML, Frontpage, table layouts, Java applets, Shockwave. You name it, they all have their day and Flash is no different. I don't know if Flash will completely disappear to be replaced by Adobe using something totally new based on HTML/CSS/Javascript libraries, or if it will just become a specialised tool for obscure websites. But there's clearly an industry-wide disliking for Flash and the momentum means Flash has certainly seen its best days.
Adobe will always be able to offer greater functionality than HTML5, but the question is whether most people will find HTML5 adequate. I think they will, especially as most complicated things *can* be done with a lot of Javascript and the <canvas> tag. Most websites won't even have to write all their own javascript, they'll just use libraries/frameworks, in the same way they currently use JQuery or MooTools.
Because HTML5 also includes offline storage and database support, it also means it's possible we'll see javascript libraries available to install on a browser rather than individual websites, meaning the user can install once and the relevant websites will just work, just like using plugins. There's already one major browser company planning something like that...