There's no 13 Reasons Why sequel
Asher's original ending kept Hannah alive. Such a twist doesn't seem doable for the adaptation, considering: 1) We see Hannah's suicide via flashback, and 2) As Asher explained to his publisher, "[Keeping Hannah alive] felt false for this particular story and for the seriousness of the issue. If someone goes through with a suicide, there are no second chances for anyone involved." The rug-pull would similarly change the tone of the adaptation, which wallows in Hannah's last days and their ensuing impact.
That doesn't mean Asher wants the TV saga to end. "I'm curious as well," the author told EW. "What happens to Clay? How do people react to what Alex did at the very end? What's going to happen to Mr. Porter? I'd thought of a sequel at some point. I'd brainstormed it, but decided I wasn't going to write it. So I'd love to see it." Fortunately, a lack of further source material isn't a problem.
The finale sees Clay confront Mr. Porter, the school counselor who had a chance to save Hannah on the last day of her life. "It has to get better, the way we treat each other and look out for each other," Clay says. "It has to get better somehow." Clay hands the cassettes, including the one that has Bryce's confession, to Mr. Porter, leaving their fate in his hands. With 13 hour-long episodes, Yorkey stayed true to the general blueprint of Asher's novel while fleshing the TV universe out with plenty of new twists, back stories, and characters.