He is dead. He existed out of time and was not part of the End Time time-strand. So while that strand of time no longer ocurs because we stopped it the leader of the infinite flight still dies. The remaining infinite dragons helped set up the events that enabled Warlords of Dreanor but did so with out their original leader. It is always possible they find a new leader but to encounter Murozond would just seem like a missed opportunity to create a new leader. Remember they were setting up Kairozdormu to be the new leader before Garrosh killed him and he was going to create a orc horde version of the infinite flight.