Sigh. I was excited over this. In a new interview for Entertainment Weekly, Scott Gimple confirmed that Morgan, played by the excellent Lennie James, will not return this season, but does not rule out future appearances.

EW: Of course, whenever we talk I always have to ask you about Morgan, played by Lennie James. Any chance we’ll get to see him again before season 4 ends?
GIMPLE: He will not be definitely in season four. Somebody misquoted me on that. Will he be on the show again? Yes. I am absolutely certain of that.

Gimple also answered many other questions, from the mysterious "Gareth" character to the Sanctuary to the possibility of seeing Lilly and Tara again.

EW: Is the storyline with Lilly or Tara or anyone from the Governor’s camp finished? Could we see any of those people again?
GIMPLE: When anybody doesn’t die onscreen, I assume it’s possible that we will see them again. Judith is a different thing — her fate most likely cannot be shown on television. I will say there are some eagle-eyed people on the internet out there who have scoured the advertisement and pre-released things and they believe they have spotted Tara. People on the internet are smart, so I’d say we’ll probably be seeing Tara.
EW: What about this other new character named Gareth I’ve heard whispers about?
GIMPLE: I can say very little. Kind of from the books, kind of not totally from the books. Comic fans would not know him. He was an invention that was inspired for the show.

EW: Let’s go through some other loose ends. Are we going to learn anything about that faint radio signal that Daryl heard in the car talking about sanctuary?
GIMPLE: Absolutely, sooner rather than later.

EW: What about the rat vivisection and zombie feeding by the gate? Will we get more clarity on who was responsible for that?
GIMPLE: I love that I can say these yeses. Yes, that answer doesn’t come as quickly though.

Lennie James, on the other hand, was cast as the lead in the 13-episode Sky1 miniseries, Critical, created by Jed Mercurio, who worked with James on BBC2's Line of Duty and BBC3's Bodies.