Saying this sounds a little weird coming out of a computer scientist's keyboard. After all, HTML is not really a programming language and it is very limited in what it can accomplish when compared to C++ and Java. And, ironically, most of the browsers that are developed for smart devices are written in C++, not HTML. C++ is still the "go to" language for writing apps that must perform efficiently at a low level. However, for the rest of the computing world (those writing apps for most business, consumer, and entertainment reasons), HTML is the way to go for cross platform compatibility...and HTML5 will only strengthen what can be done for browser-based apps.
HTML is building off the back of great work done using a C++ framework. In a lot of ways, this thought is not news...I was just pondering it on my way back from lunch today. I'm further cementing in my mind that HTML has accomplished a lot of what C++ and Java were expected to do when it comes to user interface. I'm tying back into my thoughts from my academic years from a decade and a half ago.
You don't hear "write once, run anywhere" very often any more. Maybe this is because the beautiful complexity of the internet resulting in users no longer caring where the app is run. It's running in the cloud...that magical place where developers can pick the technology of their choice and everyone can interface with it through our good friend HTML