I mean, Luke Evans really brought the whole villain role to another level when compared to his predecessors, so having him return as either a villain or an anti-hero could open a lot of doors for the franchise.
We don’t know what came of Owen Shaw after forcing Cipher’s pilot to land the plane at the conclusion of the eighth film, and he didn’t show up in his brother’s spin-off Hobbs And Shaw, so we don’t know whether he will return for Fast And Furious 9 or not, but we can only hope that he teams up with his older brother again at some point.