The counterparties to these products would still need derivatives that reference BBSW so that they can hedge their interest rate exposures. In the event that LIBOR was to be discontinued, with contracts transitioning to risk-free rates, there may be some corresponding migration away from BBSW towards the cash rate.
This will depend on how international markets for products 4/5  BIS central bankers' speeches  such as derivatives and syndicated loans end up adapting in a post-LIBOR world. The infrastructure is already in place for BBSW and the cash rate to coexist as the key interest rate benchmarks for the Australian dollar.