Here is a quick post on how to update a IPKG based zone on OpenIndiana and other Illumos based distributions.
You cannot do this from withing the zone itself but this has to be done form the global zone.

root@gravity:~# zoneadm -z zonename halt 
root@gravity:~# zoneadm -z zonename detach 
root@gravity:~# zoneadm -z zonename attach -u 

When the zone is re-attached it will be update. So the zone will be down for a few minutes.
This also made it to the wiki because I wasted a few hours trying to do this from withing the zone.