Drupal 7 development site at http://www.drupal.org/community-initiatives/drupal-core.
Other Drupal 7 planned enhancements:
Objects can declare them selves to be "field-able" - to have fields. D7 will be more "field-focussed" rather than "node-focussed".
The SimpleTest testing framework will be included in the Drupal 7 core.
A new WYSIWYG API will be inclduded to help standardize WYSIWYG integration, while still supporting multiple WYSIWYG editors.