NFS service in local zones have been frequently requested since the introduction of zones in Solaris 10, the change request for this even predates Solaris 10 by two years, it was filled in 2003. I've earlier mentioned that some works was being done to this including PSARC/2010/208. Now it seems that this has been implemented and will be integrated into internal build 154 of Solaris Next. This is hopefully in time for the first release of Solaris 11 Express which is expected next month.
Update: I was a bit quick on this one, build 154 should close in the end of next month, that does not work very well with a November release of Solaris Express, so it might be delayed or more probably it will not be part of the first Express release.
Zones should be able to be NFS servers, bugid 4964859
NFS Instances with NFS shares.
Talks I have given
5 months ago