Idea for a follow up series
Sadly, the show runner has confirmed that Dexter is well and truly dead, and would not be featured in any continuation of the series, if it came to pass.
In an alternate universe though, I would have had Dexter survive, but waiting on death row for his eventual execution.
In my series, he would become a Hannibal Lecter type... behind bars but providing advice and guidance to FBI and jurisdictional police on serial killers at large in exchange for a stay of execution.
The main character would be the FBI agent who does the actual legwork and apprehension of the serial killer with Dexter's advice. The two would have a strained working relationship obviously.
Eventually in the series -- or a follow up season -- Dexter would realize that one of the killers that he is providing advice for is Harrison, although Dexter's relationship to Harrison is unknown to the FBI. Dexter's dilmema would be deliberately misleading the police to save Harrison while seemingly not to.
Meanwhile Harrison would have no idea that Dexter is working for the FBI, that Dexter is on to him and is trying to warn him/ protect him.
I even have an idea for the final episode that I think would have worked better than what we got with New Blood. It'll all remain a fantasy in my head I guess.