Remember that Nihilus is still sentient, despite being driven by hunger he is not like a rancor who gobbles up everything. He orchestrated several elements of the Dark Wars including his alliance with Vaklu. So its obvious that Nihilus can be manipulative, cunning and use diplomacy. For that reason I don't think Nihilus would just turn on his allies and consume everything. He is capable of just consuming the Sith Emperor and being done - remember he once served Traya (I assume this would be their relationship) and had an alliance with Sion.
In short Nihilus would consume every single one of these combatants on the list and be satisfied for the next 20years or so. The only ones walking out for sure would be Nihilus and Sion since hes shown to survive Nihilus' force drain and cant die. Traya would probably survive (she has before) but im not completely positive she would.