Is there anything like official guidance which of the two terms should be used?

I see, on one hand, that an effort to replace tenant by project in keystone has been ongoing for a year or so (https://www.mail-archive.com/openstack-dev@lists.openstack.org/msg09709.html). On the other hand, in Icehouse the CLIs still use tenant, and so does the cloud admin guide (http://docs.openstack.org/admin-guide-cloud/content/keystone-user-management.html).

Sorry for the bad formatting; I don't seem to have enough karma to use URLs.