Given that Jadis’ group could be a valuable ally to Alexandria (provided that Rick gets his hands on a whole bunch of guns for them), Gabriel could be indirectly responsible for an alliance to make a stand against Negan.
Maybe Gabriel will go down as one of the big heroes of Season 7.
In the last couple of episodes, Gabriel even managed to leave a clue for Rick and Co. to come after him (and their entire pantry full of goods) after Jadis and her group raided Alexandria.