Ugh...Every time someone brings up Mass Effect, I feel like the retired renegade cop who just wants to relax, but they keep pulling him back in for one last job. Look, here's a bullet point of why a lot of people think another game in the Mass Effect universe is a bad idea:
-The stakes CAN'T get any higher. The Mass Effect trilogy already explained pretty much everything that the series' entire fictional universe was about. We just CAN'T go beyond the Reapers. The story of the trilogy encompassed everything we will ever need to know about this fictional version of our galaxy. Unless you do a full on sequel, in which case:
-You have to deal with the endings. Which means that:
--You have to choose one of them to make it "cannon". Which is terrible, because
--They're all pretty bad. I personally don't want to play a game set in any of those futures, especially not the "best" ending, synthesis, which I consider to be the worst one. Although it probably be the one they'd pick. But I guess you can always do a prequel, right?
-Nope. See Bullet Point 1. Any information or plot we're given will pale in automatic comparison to that of the original trilogy. Which isn't a bad thing, because you SHOULD compare them. They're in the same universe, and thus, are all part of the same story, whether you like it or not. So it would be really hard to get invested in a problem that is NOT Reapers when you know there's still fucking Reapers out there somewhere. (Though I will admit, it certainly isn't impossible)
Frankly, I'd rather they pull a Bioshock Infinite. You know, make an indirect sequel with plot, setting, characters, and gameplay that is similar but distinct from the game it's based on. I'd love to see another sci-fi Bioware game. Hell, I'd love to see another great Mass Effect game. But the endings make that...improbable. Though again, not impossible.