I really think that the essay touched on a moot point. Or misses a moot point, however you want to put it.
The author of the essay touched on the truth a bit--questioning whether things like gears were html competitors, even quoting google on gears being an html ally; but I don't feel like he got it. I felt like he really thought that there would be one technology to rule them all. I'm having a hard time swallowing his premise.
Flash and flash-free websites have co-existed for years; this won't change. In both cases there are advantages--there are things you can do with flash that you can't do otherwise; but doing *everything* with flash isn't prudent. Text/information is best represented as such, not in a large flash app. Plus, with the growing popularity of mobile web there are even more compelling reasons to go lo-fi, or at least offer low-fi options. It is much, much easier to maintain a hi-fi and low-fi version of a website that is primarily database/server side scripted, serving two versions of html, than it is to maintain a flash website and a text-only alternative for mobile users.
The central flaw with the essay, to me, is that it doesn't seem to acknowledge that there are different tools ideal for different applications. His mentioning of "rich applications" was a drastic over generalization -- you can't lump gmail, youtube, backpack, twitter into the same category because they're all "web 2.0". If a website is data driven; text--e-mail, blogging, note taking, to-do lists--anywhere where you may at some point want to copy/paste, have a search engine scour the text, view it in a browser that you can't install plugins in -- some form of HTML presentation is ideal. AJAX, purely server side scripted, whatever: Third party plugins aren't the way to go. For speed, resources, compatibility and a hoard of other reasons. If what you want to do is stream audio or video, it's a no-brainer, go with a tool designed for multimedia presentation. Flash. Silverlight. et cetera.
As for third party plugin technologies. . . Flash has been with us for a long time, it will continue to evolve and I don't believe it will go away. Not unless google, youtube and a wealth of other big players--not to mention web developers, game developers and the like decide silverlight is worth dropping everything and running with it. Not likely. Maybe there's even room for Silverlight in the mix, though. Admittedly, I've delved into it very little. As for proprietary browser extensions like BrowserPlus and GoogleGears? These aren't really competing technologies but additional tools with specific uses -- these have come and gone in droves over the years. Some stick around, some don't. While they may impact some users experiences significantly, they really don't impact the Internet as a whole and are by no means integral to our usage in the way HTML is. Many online services offer browser extensions, toolbars, bookmarklets, et cetera to enhance the experience and expand upon it. It doesn't mean they're rewriting every other web app in the near future.
I thought that this essay was too long for what little it really said/concluded, but was much too short for the subject matter. It over simplified a much larger non-issue.
Flash versus silverlight would be a valid essay--they are two comparable technologies vieing for the same niche. Flash versus silverlight versus gears versus AJAX? Hammer versus torque wrench versus rubber mallet versus can opener. Who wins?