Is there an upgrade path to GRC Access Controls 10.0?

Not directly.

The architecture of GRC AC 10.0 is based upon the ABAP platform and therefore it it not possible to technically upgrade from the previous versions on to version 10.0.

However, SAP have provided migration tools from the 5.3 release to aid in transfering any data that you have in version 5.3.

If you are on a previous version such as 5.2, then the standard migration path is to upgrade to 5.3 and then use the migration tools to transfer content into version 10.0.