The Web has no one who can ensure that the platform acquires cutting edge capabilities in a timely manner (camera access, anyone?). The Web has no one who can ensure that the platform makes real developers happy and productive. The Web has no one to ensure that it is competitive with other platforms, and so increasingly we are seeing developers investing their time in other platforms that serve their needs better.
The arrogance of Web evangelists is staggering. They take for granted that the Web will always be popular regardless of whether it is technologically competitive with other platforms. They place ideology above relevance. Haven't they noticed that the world of software is ablaze with new ideas and a growing number of those ideas are flat out impossible to build on the Web? I can easily see a world in which Web usage falls to insignificant levels compared to Android, iOS, and Windows, and becomes a footnote in history. That thing we used to use in the early days of the Internet.
My prediction is that, unless the leadership vacuum is filled, the Web is going to retreat back to its origins as a network of hyperlinked documents. The Web will be just another app that you use when you want to find some information, like Wikipedia, but it will no longer be your primary window. The Web will no longer be the place for social networks, games, forums, photo sharing, music players, video players, word processors, calendaring, or anything interactive. Newspapers and blogs will be replaced by Facebook and Twitter and you will access them only through native apps. HTTP will live on as the data backbone used by native applications, but it will no longer serve those applications through HTML. Freedom of information may be restricted to whatever our information overlords see fit to feature on their App Market Stores.
Let's face facts: the Web will never be the dominant platform. There will forever be other important platforms competing for users' time. To thrive, HTML and company need what those other platforms have: a single source repository and a good owner to drive it. A standards body is not suited to perform this role. Browser vendors are innovating in some areas, but they are stalled by the standards process in so many areas that is impossible to create a platform with a coherent, unified vision the way Apple has with Cocoa or the way Python has with Guido.
I wish I could offer solutions, but I have none. I know where we need to go, but not how to get there. It would help if all the rendering engines but one were to die, but even that would not be enough. Even if WebKit was the only game in town, it would still be crucial for it to have competent, sympathetic, benevolent leaders. The closest thing we have to that today is Chromium, but they have no foothold in mobile and are likely years away from having one. And so I end on a sad note.