The fact that Garrosh being deposed or outright killed not leading to the end of the war is one that just seems like common sense to me. However, it is more likely that it will just be over. Either way could lead to good story hooks in the future. I am more than sure that the Orcs will have a schism over the ending events in MoP, Garrosh *is* hugely popular with them, if not so much with the other races.