Aqua was 100% until Tiger when some hints of metal appeared in iTunes and what not. Leopard and Snow Leopard added a LOT of skeuomorphic "Metal" elements. Lion phased out metal for just plain GREY colors (very Linux/Windows-like sadly) and by Mountain Lion, skeuomorphism was dying out entirely. In Mavericks, many elements of from early OS X are still present (e.g. still have a dock; actually the Yosemite Dock is the one thing that looks more like the original than the 3D dock of Leopard, but to me that seems to be going BACKWARDS in progression. Steve liked the 3D dock. I use a side-dock so I don't really care, but I do care that it won't migrate to my 2nd monitor!).
You seem to get some of the details wrong (
when some elements appeared - the order in which they appear is somewhat correct).
Brushed metal: iTunes and QuickTime Player used the theme even on Mac OS 9. First new major Mac OS X applications to use brushed metal appeared in Mac OS X 10.2, when Safari, iCal and
iChat were introduced. The theme was more prominently featured in Mac OS X 10.3 and 10.4 when Finder adopted it. Brushed metal was completely phased out in Mac OS X 10.5, in favour of a simpler style, the "unified" style.
"Unified" style: Mac OS X 10.4 introduced a new "unified" window style, which combined title bar and toolbar into one, seamless element (was used in Mail and System Preferences). Mac OS X 10.5 adopted this style for all windows with a darker shade of grey; iTunes had began using it in version 5 (released in late 2005). This style could be considered metal too, but there was no texture - it was just a gradient. 10.7, 10.8 and 10.9 are a continuation of this style.
Skeuomorphism: Apple went wild with this direction in Mac OS X 10.7 and 10.8 - remember Calendar, Address Book or Notes? Rich textures like leather appeared in those applications at that time. So no, skeuomorphism hadn't died out by then. It was in 10.9 Mavericks when Apple got rid of these textures and returned to the standard UI style in aforementioned applications.
All of that concerns the general window style. Most other user interface elements have stayed fairly consistent throughout the run of Mac OS X (notable changes include square buttons and removal of gel scroll bars as well as some other blue elements in 10.7).
Sorry to not contribute to the topic itself at this time - I just felt I had to set this record straight. Feel free to correct me if
I got some of the details wrong. Having used Mac OS X full-time since 10.4 and studied earlier versions extensively, this should be pretty accurate, though.