A bunch of people held a meeting in California just before the last MySQL User Conference. They decided that tablespaces are not inside databases, and databases are not part of tablespaces. They are separate objects which overlap, for example table A can belong to tablespace X and database Y, while table B can belong to tablespace Y and database X. The result will be some restrictions regarding what you can do with tablespace maintenance statements, particularly for Falcon tablespaces.
The meeting participants also decided that there must be a new privilege, CREATE TABLESPACE, which will be required for CREATE TABLESPACE, ALTER TABLESPACE, and DROP TABLESPACE.
And there was talk about a new table for metadata: INFORMATION_SCHEMA.TABLESPACES.