Campaign:
-Scarab fights, maybe even a fight against a Super scarab like the one in Halo Wars
-Human air vehicles seem to be what almost everyone want. A pilotable Vulture would be amazing
-Bosses
-Bigger missions
-Brutes, Drones and Engineers
-ODST's
-Big space and air battles
War Games:
-Space battles
-A huge vehicle based map
Other:
-Ability to customize and make your own assassinations
-Flamethrower
-Dual weilding