How can HTML5 "replace" Flash?

When Steve J. made the comments about HTML5 being the future, he didn't bother to explain that this statement really refers to the most widespread use of Flash today, that being Video. Perhaps he didn't explain this purposely, so that many misinformed end users who want to watch Hulu on their iPhones would unleash their rage against Flash. Which is exactly what has been happening..It is annoying and I lost respect for Steve.

The HTML5 stack (html, css and JS) will NOT be a direct replacement for Flash. I have been developing Flash content for over 10 years, I am also very competent in JS. I cringe thinking about using JS for tasks where ActionScript can accomplish the same thing in 50% less code. There are tasks that will be very difficult if not impossible to achieve with JS and CSS. For rudimentary animations and JQuery-like functionality, sure, HTML5 can be a viable option instead Flash. But for complex games and RIAs, I just don't see it. Actionscript has evolved into a robust, full featured language.

The other important thing is that the Flash player is updated by Adobe periodically to address any issues that may arise. How will they update/improve HTML5 spec if it becomes the norm and Flash went bye-bye?? They won't. You have to wait for HTML6 and all the browsers to support it. Which means you end up waiting 5-10 years. Great way to bring us back to 1998. No thanks, I'll stick with Flash for now.

As much as open standards are a worthy goal, I don't see this panning out the way they are saying...

My two cents.

I think some people here are programming snobs and aren't listening. I, too, am a beginning Flash developer and I don't want it to go away. You know why? Because CREATIVE people can use Flash to develop what's in our brains very easily. A person who likes to draw and create scenes does not necessarily like to code. Typing a bunch of "sentences" is NOT drawing and animating! What you're saying about HTML5 is like saying that Picasso and Dali should have learned a programming language in order to paint. Ridiculous, right?

That's why people prefer Flash to HTML5. It's not self-serving, it's just acknowledging that the people capable of creating cool animated web content would rather be able to create our own visions rather than learn an unrelated skill or rely on someone else to interpret for us.

Instead of ridiculing, you might want to come up with an HTML5 visual environment that rivals Flash.

how it is possible from a technical/coding point-of-view that a text-based markup language (HTML5) could be considered a replacement to a multimedia framework (Flash)?

HTML5 is the new hot name for "web technologies stack", not just a "markup language".

It has a programming language (JavaScript), like Flash does; a set of APIs, significantly expanding as part of the efforts commonly labeled as "HTML5", ways to draw graphics (SVG, <canvas>), play audio and video (<audio>, <video>).

Unlike Flash, the "HTML5 applications" are processed by the browser, not by a proprietary browser plugin, which is good - at least for browser vendors (see the relevant piece of this blog post - thanks Jotham). For example, it makes possible for a browser vendor to fix issues (and not wait for Adobe) -- IIRC Apple cited Flash as being #1 reason for crashes among all crashes on the Mac.

[edited to remove "open standards are better" claims which I am too lazy to back up]