I just picture the ending like this....... Eddie is handcuffed, walking down the prison hall, other prisoners are glairing at him, making comments, the guard opens the cell, Eddie walks into it, they uncuff him, he looks over and sees a bunk bed, someone is laying on the bottom bunk, the cells dark, he can't make out who it is, all a sudden the prisoner sits up, and lights a cigerette, he looks over at Eddie... the prisoner says "who the hell are you"........ Eddie looks at him, "my name is...... Brock, call me Brock"......... the prisoner stands up and exits the darkness, clost up of his eyes, then to his mouth, he's taking the ciggerette out of his mouth.... pull camera back...... the prisoner says "I'm Cletus Kassidy"...........
show a quick flash of lightening from outside, when the light from the lightening hits, show on outline around him of a carnage, only for a second.... roll credits....
it doesn't imply that the symbiote attached itself to Cletus yet, it's just forshadowing for a possible sequel, and it's a nod to fans