I would love it if the Arbiter appeared at Earth and become allies with humans again and then go to Requiem with the good covenant fleet and they fight Jul M'dama ( big boss fight at the end) meanwhile the Prometheans attack Earth while Chief defends it with the Infinity. the Didact managed to survive the events of Halo 4 and he leads the Prometheans' attack on Earth.
Also, on installation 05 during Halo 2 the flood were on the ring but were never eradicated. Has everyone else forgotten them or were they destroyed or are no longer a threat?
