A successful joint operation by the two legitimate governments will have an additional benefit besides finishing once and for all the vengeance for the dead...
Defeating the Interahamwe will remove the major "legitimate" reason for the continued existence of General Nkunda's CNDP Congolese Tutsi renegade army. Doing that will then set the standard for him laying down arms (because his "cause" won). If the CNDP doesn't come in from the bush then, it becomes pretty hard to argue they aren't just another thieving band of resource pirates, and maybe then someone will actually do something about the fighting in Kivu.
... don't count on that somebody being the U.N. however:
The U.N. mission in Congo said it was not associated with the operations but confirmed that the Rwandan forces had entered Congolese territory.