Why can't it be both? Applications are still, in essence, a type of interactive view hierarchy of document. The web can serve up both types of data: document-b

Why can't it be both? Applications are still, in essence, a type of interactive view hierarchy of document. The web can serve up both types of data: document-based (e.g. Wikipedia) and application-based (e.g. Gmail). Being able to have a core toolchain of three inter-related languages that can communicate with each other that you can use as required should be the final goal. For instance, if you're writing a web application, you could only use CSS/JS, and if you needed to write a very simple blog, you could use all three, or just HTML and CSS. Having more options never hurt anyone. Better JIT of JavaScript code would break pure JS open, allowing full apps to be written without language fragmentation. Those who will still require stylesheets can use them as they wish. It's a win-win situation on both ends.