Even though this directory says wheezy the image here is really just a pre-release version (basically using wheezy in /etc/apt/sources.list instead of testing) this means you will be tracking testing until wheezy is released. When wheezy is released I will try to update this image with an actual release version and either delete this README or update it to reflect that fact. There should be a post on powerdeveloper if that happens in either case.