John Gruber, linking to this article on Macworld:
What this piece made clear for me is that (a) something similar is going to happen to Mac OS X, almost certainly this year; but (b) there’s no way to look at iOS 7 and predict what a corresponding refresh for Mac OS X will look like. Maybe the only things I’ll predict are lots of white backgrounds, and Helvetica Neue as the system font.
As I wrote in my Mavericks review, I think previous design experiments in this realm haven’t been great, but I do think it’s time for Apple to apply some fresh paint to OS X. For the most part, Mavericks looks very similar to Leopard.