According to recent comments on BioWare's official Mass Effect forums (via NeoGAF
), the director of BioWare Montreal, Yanick Roy, has revealed that the studio doesn't want people calling their next title Mass Effect 4. Roy states that "thinking of the next Mass Effect game as Mass Effect 4 would imply a certain linearity, a straight evolution of the gameplay and story of the first three games."
While it isn't clear what kind of timeline or story the next Mass Effect title will be based on, Roy has confirmed that it won't necessarily be a straight prequel or sequel. The director also detailed that while it won't be based on the current storyline, the previous three games will be recognised but likely won't be the main focus. He also reassured players that what makes Mass Effect "is indead the alien races, the technology, the lore, history, etc. You can safely expect those in the next Mass Effect."
Currently no date has been set yet for the next Mass Effect title, however Roy did reveal that while a Mass Effect MMO isn't impossible, it is not the currently in-development title.