WCCP VRF Aware support is part of the WCCPv2 enhancements. Sup6-E does not support WCCPv2 to begin with.
When WCCP VRF Aware support is finally available on the 4500 platform, I would expect Supervisors other than Sup6-E to have it first.
At the moment, it's not in the roadmap.
Regards,
Edison