Very vague, but it seems it will be possible to use different storage than SQL Server, probably starting with SP1. Might it be in conjunction with SQL Server 2008 Katmai?

http://support.microsoft.com/kb/938499/

Some Posts:

http://www.21apps.com/2007/06/sql-server-2008-helping-sharepoint.html

SQL Server 2008 - Helping SharePoint Scale cost effectively