The general CSS class scheme is there. The master templates are in a state of transition at the moment, and we'll be changing the way packages pass header information and some other stuff in oacs 5.4, due for release this fall (early, I hope).
Compatibility master templates are provided for existing sites, but eventually we'll probably say "if you wanna upgrade, you gotta upgrade [everything]".
Check out the oacs-5-3 branch and install a test site if you want to get an idea as to where we're going.
