The character in Dexter is someone who has suffered childhood trauma and cannot feel emotion. Does he go to Hell?
TV Series like Dexter are PR for the Anti-Christ. They take a very bad guy, and turn Him into a Hero, that way people start to think that "sometimes North is South".
There are Vampires who are portrayed as lead Characters from Soap Operas, that is fantasy, but more of the same anyway. "Evil could be good" seems to be the indoctrinating lesson for the masses to learn.
The list of Films or TV Series using this same recipe could be very long, but what I find interesting is that this "sudden twist" on story writing is quite recent.
I remember my childhood, back then, Vampires, Zombies, Werewolves, and demons were all always the bad guys, and there were NO exceptions. We just looked forward to see them killed, there was no dialogue, no conversion, no middle way, just a stake to the heart or a silver bullet.
Those days are gone, and something very bad must be coming soon. I think the masses are being quickly and intensely indoctrinated, so they would accept the worst bad guy ever.
And my answer is YES, Dexter would wind up on a very warm corner of Hell.