The bit inside the 'cmsplugin' tag is actually a link plugin!

embedable_plugin.py

class LinkPlugin(CMSPluginBase):
    def get_embed_content(self, instance, parent_instance):
        ctx = Context()
        return render_to_string(self.render_template, self.render(ctx, instance, None))

gistfile2.txt

new-cmsplugin-admin-editor.html

<p>
Some normal text. <cmsplugin pluginid="123"><a href="http://www.djanog-cms.org">django CMS website</a></cmsplugin>.
</p>

new-cmsplugin-database-representation.html

<p>
Some normal text. <cmsplugin pluginid="123" />.
</p>

new-cmsplugin-frontend-representation.html

<p>
Some normal text. <a href="http://www.djanog-cms.org">django CMS website</a>.
</p>