It occurs to me that I haven't heard anything about how SQL access will work with a multi-tenant database in 11.0. Is there going to be a SQL equivalent of Client-Principal?
SQL will use its regular login mechanism to access the database as a tenant with the extended user id (userid@domain). There is no client principal object like thing needed.
So, that login will establish it as a regular tenant or a supertenant?
Yes, based on the tenant associate with the domain specified after the "@" sign the user will establish the desired tenant identity once authenticated.
There will also be a set of DDL extensions to support multitenancy. DDL is mostly non standard in all the datbases anyway.
There won't be a lot in the way of DML extensions.