It won't be, but it should be a completely different genre. That universe is so full of amazing possibilities (even if my enthusiasm for it has wayned) that it would be criminal to stick to the same gameplay. How about a turn based strategy game, civ style, where you play the Mass Effect universe. Choose your race, and shape how it develops from the end of the Prothean cycle. Maybe humans reach their relay before the Asari? Who knows?
Or even a Character Action Game as a justicar, or a space combat game with Joker, or a detective story set on the citadel, or bloody anything!
Turn-based tactics like XCOM! Man, I would play that game!!!
I would totally play that game. Best part: You get to choose what race you want to play as. BOOM!