We're going to avoid updating wp-content on update. The exception is if an update crosses a version that introduced a new default theme, it will be copied over.

Initially, we're not unbundling anything. (And keep in mind Akismet is already an external to plugins.svn.)

The plan will be easy to implement and it's going to be really effective. No more Akismet dances, and themes won't get overridden in a core update.