BioWare says Mass Effect 4 due "late 2014 to mid-2015"
[UPDATE]: We have received an update that Gamer Syndrome in fact neve spoke with anyone from BioWare. The Gamer Syndrome interview has been removed due to an "inaccurate source." Usually no news is good news, but I wanted some news, so I'm kinda sad. So no word from BioWare on anything regarding Mass Effect 4.
The Mass Effect team at BioWare is a month or two into full development for Mass Effect 4. Mass Effect 3 producer Mike Gamble spoke with Gamer Syndrome about the fourth major installment in the sci-fi series, telling them "You'll hear more about the new Mass Effect game in 2013."
Well, yea. Obviously. There is no release date, however. Gamble commented that it'll launch in "late 2014 to mid-2015," adding, "I honestly can't tell you an exact [date] because full development on the game started a month or two ago." In the meantime, there's at least one more DLC for Mass Effect 3 coming, and multiplayer will continue to be supported, as promised.
Personally, I would like to see Mass Effect 4 be a prequel -- mainly because I don't know how they would do a sequel. The problem is that Shepard started the story with the humans, so a prequel shouldn't have humans in it. Also, it would have to be 50 thousand years before the first Mass Effect, before the Protheans were wiped out by the Reapers. I would imagine anything in-between would be quite uneventful, as there was no other big threat to the galaxy.
So, we are still two years away from the next Mass Effect installment. Luckily, we're only a few weeks away from 2013, so keep your ears open for details.