[development] versioned schema?

A quick thought in terms of the Schema API and writing system/module updates: As far as I understand, on e shouldn't use functions like drupal_install_schema() in update functions since one cannot rely upon which version of the schema presently exists int he .schema file. To me this suggests that there should be a way having several different schema in the .schema file with different version numbers. Then functions like drupal_install_schema() could take an optional argument for the schema version. Does that make sense? -Peter