Commander Shepard, hero and savior of the universe, and protagonist of the original Mass Effect trilogy, will not be making a return in the fourth major iteration of the series.
Speaking to Complex, Mass Effect trilogy lead writer Mac Walters explained that he wanted to move the series on from its beginnings and to "tell a story that doesn't relate necessarily to any of the Shepard events at all, whatsoever."
“That’s what we’ve been deciding for a while,” Walters continued. “But throughout it all, one of the key things is that it has to be Mass Effect. It can’t just feel like a spin-off. It has to feel like a Mass Effect game at its heart, at its core. Just without the Shepard character or the Shepard specific companions.”
In other words, Mass Effect 4, the next Mass Effect, or whatever BioWare is calling it, will be about a completely new story set within the setting—independent of any of the characters from the original trilogy.