Bioware has stated the Mass Effect 4 narrative won’t be speaking anything of Shepard or the events that surrounded him, instead telling a story completely foreign from those events and persons.
During an interview with Complex at the New York Comic Convention, lead writer for the game Mac Walters discussed the idea of a Shepard-less Mass Effect, “Well, I can’t get into details, but the idea is that we have agreed 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. 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.”
Source: Complex