Portal is built on top of a portlet container. As of Portal 2.6, the portlet container that Portal is built on is not available separately. Portlet Container 2.0 is the JSR-286 compliant portlet container on which future versions of Portal will be implemented, starting with Portal 2.7.
It is not currently possible to upgrade the portlet container used by JBoss Portal. It will be possible to do so starting with Portal 2.7 (though only some configurations will be officially supported).
Thank you for the quick reply. That helps!