I finally managed to get a productional ipv6 address space that replaces my old 6Bone testing allocation. It was kindly provided by JOIN. Just to mention.
I do not know when 6Bone is finally shut down, but it is time to change, I think. However, all npw.net services are again reachable through ipv6. Additionally, I have added AAAA records to all the other *.npw.net subdomains this morning.
Free 64-bit ipv6 subnets are available at tunnelbroker.net.