The announcement came at a special memorial for Pratchett held at the Barbican on April 14th. Although originally reports indicated Gaiman had previously said he wouldn’t be doing anything further following Pratchett’s death, but changed his mind after receiving a letter from his fellow author, intended to be read after his death, Gaiman has clarified the situation in a blog post: “it was more of a last request while he was still alive. (“I would very much like this to happen, and I know, Neil, that you’re very very busy, but no one else could ever do it with the passion that we share for the old girl. I wish I could be more involved and I will help in any way I can,” he wrote, once I said yes.)
Good Omens was previously adapted for radio in which Gaiman and Pratchett both cameoed.
A feature version of Mort is also in the works, with a script by Pirates of the Caribbean’s Terry Rossio, as well as a TV series based around the Watch.