Last week we took a look at initial design mockups for Firefox 3.7, and now the busy designers at Mozilla are back with some theme mockups for the even further-into-the-future Firefox 4.0.
(Click any of the images for a closer look.)
They're also looking at consolidating the Stop, Refresh, and Go buttons to save a little extra space in the toolbar—similar to a user chrome tweak we've been using for quite a while.
Keep in mind that all of the changes you see here are not final—they're just exploring different ideas for upcoming releases of Firefox. Similarly, it'll be quite some time before either Firefox 4.0 or Firefox 3.7 hits servers, so if you like the basic look but want to get it now, here's how to make Firefox 3.5 look like Firefox 3.7.
Firefox/4.0 Windows Theme Mockups [Mozilla Wiki]