I really hope that's not the case. Like he ends up teaching the black guy how to use the force like Yoda to to Luke, or he teaches the girl who's more likely Leia and Han's kid.
If the First Order rose up right after the Empire, Luke likely would have gone searching for other Jedi or potential Jedi. If there's a full blown war on the last few, going into hiding could be a way for him to bide his time until some new ones arise. Or he could be actively searching.
Either way, evil Luke would be a twist for the sake of a twist. It would make absolutely no sense within the framework of Star Wars and could doom the new trilogy. Luke is not Anakin. At all. It would be obscenely out of character. Some idiots just want to say "Oh wow!" and don't give a freak about good storytelling. It's Star Wars, not a shitty campfire story with a big reveal.