According to http://boards.openlinksw.com/support/viewtopic.php?f=14&t=1204, IPv6 support will be included in the commercial release of Virtuoso. This is a feature request to also include it in the Open-Source edition.
This will be rolled into the Virtuoso Open Source release at the appropriate time.
I recently did some preliminary work in this area which might be of interest if somebody has an urgent requirement.
I'm not sure yet whether OpenLink will want to use any of my code or their own implementation, but for Ubuntu users at least there is the option to use my experimental packages: