The data can be migrated to any suitable system using
Pentaho Data Integration or similar (I am gaining experience with it at the moment).
Also, if we move to a system with a SOAP/XMLRPC API (or similar) for the back-end, another service (hosted/managed by someone else, maybe) could provide access for older/mobile browsers without impacting the design of the primary site.
jaminJay
"Just sayin'..."