The Arbiter and his faction of troops will more then likely ally with humanity or at least sgt. johnson and is troops. after all as far as we knw theyr still stuck on delta halo. So they would have to work together to find a way to Earth or wherever else. as for elites as a whole its hard to say if they will ally with us. If they do it will be a very unsteady alliance b/c the elites are very noble beings they would not take kindly to all of a sudden joining there enemys, however if arby can convince them that the prophets are false and that an alliance is best for them they may do so.