Yeah I've been speculating that they'll betray Rick for the guns, but never thought about them possibly joining Negan. If that happens I hope the Saviors wipe them out afterwards. Just to show how miniscule of a threat they are. The Junkyard group brings little to nothing to the story, imo. I never trusted any of them since their introduction, which was baffling why Rick would so easily. Normally it takes some time for new people/groups/communities to earn his trust e.g. Michonne (back in Season 3), ASZ community, Gabriel, etc. I know he was desperate for recruits but unlike the ASZ, the Hilltop, and the Kingdom he never questioned the junkyard group's skills and capabilities. Rick will look like an idiot if Jadis betrays him b/c she's obviously deceitful. She also has an ulterior motive joining a fight she and her group doesn't have any stake in.