Apparently all of those Mass Effect-related tweets this past N7 Day wasn't just BioWare employees teasing fans. According to a report, the studio is working on a fifth Mass Effect title.
According to Kotaku, BioWare Edmonton--the studio responsible for developing the Mass Effect and Dragon Age series--is "in very early development" on a new Mass Effect game. The project is being led by BioWare project director Mike Gamble--whose previous work includes serving as the producer for Mass Effect: Andromeda and lead producer for Anthem.
Let it be a Mass Effect prequel set in Shepard's timeline. I would buy it day -1 if it's based on the contact war between Humanity and the Turians.