I think the biggest holdup for faster adoption is that all the big players like Google and Apple and Micrsoft are holding off on better support until they can figure out ways to twist this open standard to their own ends. Apple hopes to use it to kill Flash. Microsoft wants to make it just another extension of their web development product line. Mozilla is hoping to they'll finally figure out a way to make some real money from all this. And Google...well... who knows what Google is up to? Their 'official' story changes almost every other day.
I personally think HTML5 will be the battleground. And HTML6 will be what eventually emerges as the "new" new web coding standard. I'm thinking that will be sometime around 2017.
I think you're bang on there.
But, I'm not sure if HTML6 will be that soon. It will take a few years for HTML5 to reach "adoption" level at this rate.