If DJ gets rid of the last couple of B737 "classics" then would they have to use a B73NG simulator in lieu of the ex-AN "classic" sim. It certainly wouldn't be fair on crews to do their licence renewals in a sim that is considerably different to the aircraft that they fly.
When the QF NG sim comes on-line, I believe that it will be heavily utilised doing a large amount of conversion and cyclic training for QF crews so I doubt if DJ will be able to rent capacity from QF and the Boeing Flight Safety/Virgin complex in BNE won't be up and running for a couple of years yet.