I really don't want a re-match with Greene...
While a "Wrath of Khan" scenario with Greene would probably not go over very well (as most people would be more interested in Quantum's numero uno), if he's still alive, and still working with Quantum, then technically he's unfinished business. The events of QOS would have put Quantum in roughly the same situation SMERSH was in in the book version of FRWL (they need to neutralize they guy that's been doing so much damage to their organzation, and do so in a way that deters future threats to their solidarity). If Greene is still alive, then he would be part of their plot to kill Bond "with ignonomy." If he's not, then his death would be yet another reason for them to want Bond dead/dishonored.