BioWare's digital store showed a store with a description suggesting Shepard's return in Mass Effect 4. Although this is not yet a fact, as there is no announcement from the developers, who I am still committed to the development of Dragon Age 4.
As shown by a YouTuber, MrHulthen, there appears to be a synopsis a linked poster from Mass Effect 4, which seems to indicate the return of Shepard, the undisputed protagonist of the trilogy. The synopsis is:
The show goes on. Shepard's final adventure may have ended with the threat of the Reapers but at the cost of the Earth itself. While Shepard and the survivors have remained scattered, fans are wondering what comes next.
Soon after there was a change, where it was omitted the presence of Shepard from the game. It is unclear whether the original text revealed information that should have remained secret outside the development team.
If you've never played Mass Effect 3 and don't want any spoilers, stop reading now.
What makes Shepard's potential return interesting is the fact that in 7 of the 8 Mass Effect 3 endings, they all die. Some of the players they must have seen Shepard sacrifice himself to stop the Reapers. But there are others, very few players have seen the ending where they live. So the hope that Shepard is in the new Mass Effect is there.
Obviously nothing is official, but fans have always speculated based on the events of Mass Effect: Andromeda, because they seem to indicate the possibility that Shepard is still alive, it could really be something canon.
It must be emphasized that all this is speculation and information not confirmed by the game's developers. So to find out if Shepard is really coming back or not, just wait for BioWare or Electronic Arts to make themselves heard.