Here's an older mockup (that dates back to July, 2010):
As you can see, the statusbar is missing in the new mockups (first and last images in this post), - in it's place, there's a temporary (only shows up when needed), overlay status bar. Once again, Gnome and Ubuntu go hand-in-hand, trying to implement the same thing but in a different way, because Ubuntu might ditch the statusbar (but not just in Nautilus) too, this being the main reason why Mark Shttleworth proposed the Windicatos.
While removing the statusbar may sound like a good idea in most applications, it doesn't feel right to do it for Nautilus because in such an application it holds very useful information like the size of the selected file(s) and so on. But of course, these are just mockups which don't show the exact functionality of the new overlay statusbar.
What do you think?