It is possible that IPv6 support would be useful in nfs.
Supporting it for the kernel side of things should be fairly straight forward. We just need to create other sockets to bind to IPv6 addresses, and we need to not assume that host addresses for 4bytes everywhere.
The user-space side would be a lot more work, particularly getting portmapper to handle IPv6. Probably the first implementation should avoid portmapper and give fixed port numbers to mountd, statd etc.