I am going to commit first part of major theme changes today. It is relatively large patch touching many areas. I would like to ask for a bit of patience because there will be several regressions that will be fixed later this week.
This week we are going to work more on internal changes, such as YUI2+YUI3 integration, navigation refactoring, outputlib improvements, etc. I will have to update the docs site too.
I suppose sometime next week the HEAD should be ready for the actual development of new themes. I will keep you informed here.
You can watch progress in tracker, see MDL-20204 . Thanks for your patience, these theme changes may hurt a bit I am afraid