I think so too.

I can see them doing a comic to wrap things up if there's enough of a demand.

I wish that was explained before the show was cancelled.
If it's all the same to you, I'll have that drink now.-Loki (Marvel's Avengers)

If Agents of SHIELD somehow makes it to Season 5, Sharon should appear and they can craft some kind of storyline where she finds Michael's journal that is important to something going on in the present. We get answers about Jack, Peggy and Sousa, and whatnot, and it could be a fun Indiana Jones-esque mini-storyline.
Stephen Dillane for Sinestro.

My money is on Michael Carter. He's actually alive and the "M. Carter" in the redacted file was referring to him. The file needed to be retrieved because he's supposed to be believed dead.
This will also allow for him to be alive decades later so he could father Sharon.

God bless America and the "Ignore this User" link.

I think it was pretty obvious that the RoboCop dude shot him because Jack betrayed him.