I completely fail to see how the release of iPhone "helped to radically increase the number of phones with Flash support". If it did help something this is to realize that we can do just fine without Flash.
So no, you don't need to wait ten years before HTML5 arrives, it is already on your doorstep (have you seen Google Wave?). There will be no wait, so "during that wait, Flash becomes more and more powerful" doesn't come to fruition. Adobe still cannot make Flash to run without hogging resources on anything but Windows, do they think I will buy this "more powerful" crap?
I don't think that HTML5 will kill Flash though, but if it forces Flash out of the places there it does not belong (full flash sites, flash navigation, etc.) Web will be a better place and I will be a lot happier.
That said, I'm all for HTML5. Whenever YouTube officially supports the video tag, I'll me more than happy to uncheck that "Enable Plugins" on my browser preferences.
So, yes, youtube is interested in HTML5 video, for the same reason google is interested in Chrome.
Why should the "open web" depend on Adobe or any one company to do something you need?
Every modern PC or Mac has Flash. Developers and, more importantly, "webmasters" (implying lack of technical skill) can rely on it being there.
OK, so the iPhone doesn't have Flash. How many web pages are broken really? Much fewer than you'd think. But even when broken pages affect the average user, they don't think "Damn you Adobe!" nor do they say "The people who run this site are stupid!" and they certainly don't blame Apple who makes this device they love so much. Believe it or not, the average user immediately assumes they personally did something wrong or are completely unsensitive to the problem. "Hmmm, I guess this page doesn't work on my phone... I'll show you later."
Openness solves engineering problems. Users don't understand engineering problems. More over, openness solves FUTURE engineering problems. Most people aren't sensitive to problems affecting them tomorrow, much less problems affecting the greater web community 5 years from now.
All I was trying to say that is that the average person is not sensitive to the same problems as "us". Flash isn't going to die because too many people just don't care about what we see as wrong with it.
On a side note: Personally, I'd rather see Flash go open than die. I value competition.
Mine don't, and not through (my) choice. And neither do either of my phone handsets (Freerunner, HTC Dream). Flash is a pain in my arse.