https://tvline.com/2020/11/20/black-lightning-cancelled-season-5-the-cw/

A week after announcing that a Painkiller spinoff (https://www.primetimer.com/item/The-CW-planning-Black-Lightning-spinoff-Painkiller-wMSmB7) was in the works, showrunner Salim Akil said Friday that Black Lightning will conclude with the upcoming Season 4. “When we first started the Black Lightning journey, I knew that Jefferson Pierce and his family of powerful Black Women would be a unique addition to the super hero genre,” Akil said in a statement. “The love that Blerds and all comic book fans around the globe have shown this series over the past three seasons proved what we imagined, Black People Want To See Themselves in all their complexities. Thank you to the phenomenal cast, writers and crew without whom none of this would’ve been possible. I’m incredibly proud of the work we’ve been able to do and the moments we’ve been able to create in bringing DC’s first African-American family of super heroes to life for the culture.” Akil added: “While Season Four may be the end of one journey, I’m extremely excited to usher in a new chapter and continued collaboration with The CW as we tell the story of Painkiller.”

Black Lightning creator: We always intended to end with Season 4, but I had ideas for a fifth and sixth season (https://deadline.com/2021/05/black-lightning-series-finale-salim-akil-interview-spoilers-painkiller-future-1234763226/)

Salim Akil says the plan always to end with a fourth season, even before the pandemic. However, he tells Deadline, "we’ve always had ideas for a Season 5, or a Season 6. We’ve always had places that we want to go. I always plan like that. I never wait; I’m always thinking about the next season. So, we could have gone on to a Season 5. We’ve had so many stories to tell because there’s so many stories out there." Since the Painkiller spinoff is dead, Akil was asked about other potential Black Lightning spinoffs. "I think that if there was a possibility, the possibility would land in Thunder and Grace and Lightning," he says. "I think that that could be a wonderful show. People would be familiar with the characters, be familiar with their backstory. They would be familiar with their wants, their needs and their goals. I think that that trio of women are just very dynamic and talented, so I could see something like that, for sure."