As @Cags said, this is not (easily) possible because the ACL tree is loaded when the session is initialized (AKA when the admin logs in).
A possible workaround would be to override the
_isSectionAllowed method in system configuration controller: (
Mage_Adminhtml_System_ConfigController::_isSectionAllowed) and make it reload the ACL tree.
protected function _isSectionAllowed($section)
$session = Mage::getSingleton('admin/session');
$session->setAcl(Mage::getResourceModel('admin/acl')->loadAcl());//reload the tree
return parent::_isSectionAllowed($secntion); //all the code from the original method
But this means the ACL tree will be reloaded every time you access a config section. I see no point in doing this.
Also you cannot do it for one specific extension. You will have to rewrite the core class.