That said, Doctor Strange 2 has not been officially announced yet and if director Scott Derrickson does return as he hopes, he and writer Jon Spaihts already seem keen on featuring Nightmare as the villain.
Even though Marantz’s designs were not used, it will be interesting to see if any future Doctor Strange movie sequels utilize portions of his designs/concepts, should Dormammu ever return.
Still, Dormammu is a villain after all and staying true to their word is not necessarily something that they are known for doing.
This could leave Dormammu in the Dark Dimension for a few more years.