A discussion that started a few days ago on the mozilla.dev.planning list has given birth to the idea of taking all this one step further by building a complete Desktop Environment, like gnome or KDE. Such a thing would then be based on XUL (XML User Interface Language) and it sounds like a very potent venture. This would then include expanding the features of, for example, Firefox to give the browser the ability to do local file management, just like Konqueror.
This is a solid idea, I admit. Though, most ventures like this seem to have a single goal in mind, in this case it would revolve solely around Mozillas own products. Even still, it might not be such a bad thing to see this in development.
Source: Nordic Hardware