Notes from yched's speech at the Paris core code spring 2012/04/28-29. Use with caution after 2012/05, fast moving code:

• A “Plugin Type” is a class.
• The list of existing plugins of a plugin type is enumerated using a Discovery class
• PluginTypeFactory implements FactoryInterface
• PluginTypeDiscovery implements DiscoveryInterface
• PluginTypeMapper implements MapperInterface
• DiscoveryInterface::getDefinition($plugin_id = 'textarea')
• DiscoveryInterface::getDefinitions()
• ?::createPluginInstance()
• ?::getPluginInstance(array $options = array()) ← think service locator
• $plugin→set(….)

Code under development in EclipseGC's sandbox at http://drupal.org/node/1441840 branch: plugins-next