The actress has been confirmed and the actress who will portray Lucille confirmed it herself. About the movies, they discussed about it, never confirmed that the films will be made. Also, they don't have to do a movie about what happened to Negan before the apocalypse and during the apocalypse before he met Rick. They could easily and possibly do a movie about what happened to him after the Whisperer War, where in the comics, he left Alexandria and we thought that we will never see him again until the release of Issue 193. So in short, they could do a movie about that time period that we didn't see in the comics. Also, check my new discussion post about the episode titles of 10B, I want to know your opinion about it.