5. The Galaxy Has Changed
Regardless of how you've played your character, the countless situations which could be explored in a sequel are vast. For instance, the Krogans being cured of the Genophage, whilst the Salarians intended sabotage of the curing mechanism was revealed to Wrex, and also the fragile peace brokered between Geth and Quarians. These are two situations which can spiral in multiple different ways like the Krogans declaring war on the Salarians for the genocidal intentions, or how advanced both the Quarians and Geth have become with helping one another, for instance the Geth strengthening the Quarians immune system. This is but one event which could add a different complex world for the sequel, like how Earth could still be recovering from the war because Shepard to bringing enough war assets or the lack of alien influence in governmental decisions because of Shepard being a racist. There are dozens of possible scenarios which leaves many questions as to how potentially diverse the future will be for the sequel.