I can't really picture the return of the arbiter other then getting revenge on jul for the attempted assassination.
The elite have always been the superior units in the covenant forces and i don't see that changing anytime soon.
What i want from Halo 5 is to discover precursor technology being that the forerunner tech was tier 1 imagine what the precursors had being a tier 0 race.
The campaign in halo 4 was amazing i'v grown up with the game and i love the emotional twist with the death of Cortana. Can't wait for the campaign of H5 hopefully we will get to see a side of chief that we haven't seen before