This is more of a feature request than a problem. I have recently enabled IPv6 on my network and would like to enable IPv6 on my NAS, and I realize that there are no configuration options to do this right now. Even if it just was a stateless configuration client, and I was unable to manually set the IPv6 address, I would be happy.
Samba has fully supported supported IPv6 since v3.2 (link here.)
For those of you more curious about IPv6, and how to get it on your home router or PC, please visit http://www.tunnelbroker.net/ for free IPv6 connectivity. Visit their forums for help with setting it up.