Firefox may not be going on the right path…
Unfortunately, all the browser developers are copying one another to some extent, it just shows lack of originality from all UX teams.
The mock-ups in the article, are for the moment, just that and you can Download a UX build to see the early interface changes that may or may not be included in later release builds. There’s also a theme for other versions of the browser available here
In the end, for firefox at least, it doesn’t matter what the designers do to the interface, as it’s only CSS and can easily be changed.