I do think they will have him make a small cameo, but what I am talking about is having him come back for the better part of the season or at-least a couple dedicated episodes for him. The writers aren’t dumb, they know Rick is TWD and would be stupid not to “cash in” on his return.I think your prayer has a chance.
With the dwindling popularity of the show I doubt they'll invest in Grimes movies. I havent heard anything of them going into production. I could see them bringing him back for a couple of cameos as they know its the final season.