As functionality gets added to the StackExchange family of sites, the horizontal menus start to become crowded. In fact, the top navigation bar (stack dropdown, username, about, faq...) was frozen by Jeff some time ago.
This means that some very interesting options get hidden. For instance, the blog is hidden way under the fold.
It's possible to improve the design of the site by using the 'mega-menu pattern'.
Where each element should be placed in this menu is something to be thought about, to be sure.
The question is whether the current design is still capable of accepting more functionality and, if not, whether the 'mega-menu pattern' would be the best replacement for StackExchange.