Same here, as far as I heard during the CEP the databases will be integrated in the db’s we already have in SCOM.
Check out the deployment topology screenshot in this post:
http://www.bictt.com/blogs/bictt.php/2011/10/04/scom-2012-cep-meeting-five
So the write actions going to both scom databases and the advisor/diagnostics and so on will pull data from serveral sources as needed.