No, it does not support the datastore. Now you do not have to distribute your own zipfile of Django 1.2.5. The word 'supports' does not refer to Django integration with the GAE api's, but rather that this new version is available on the server. Django 1.2.5 was added so that you can load it via use_library, but it has not been altered in any way to support the GAE api. So you still have to use the google-app-engine-helper to apply monkey patches to make Django useable.
If you are using Django 1.3.0 alpha 1 you are probable either using your own zipfile, or django-nonrel. In either case, you should not have any issues with the 1.2.5 use_library feature because you were not using it.