Whilst Shepard’s story has reached conclusion, the vast Mass Effect universe is open for exploration and Bioware believe it does the series a disservice labelling it ‘Mass Effect 4’.
“To call the next game Mass Effect 4 or ME4 is doing it a disservice and seems to cause a lot of confusion here.“We have already said that the Commander Shepard trilogy is over and that the next game will not feature him/her. That is the only detail you have on the game. I see people saying ‘well, they’ll have to pick a canon ending’. “No, because the game does not have to come after. Or before. Or off to the side. Or with characters you know. Or yaddayaddayadda.”
Yanick Roy chimed in soon after adding that “That doesn’t mean that events of the first three games and the choices you made won’t get recognised, but they likely won’t be what this new story will focus on. “What makes it Mass Effect is indeed the alien races, the technology, the lore, history, etc. You can safely expect those in the next Mass Effect.”
This suggests the decisions made in the series thus far could have an impact in the sequel to Mass Effect 3 (since we can’t call it Mass Effect 4). However with details so thin on the ground, it’s nothing more than speculation, especially since Bioware could throw a spanner into the works by announcing a prequel.