Maybe he joins the Seven Solders as a roaming multiversal Magnificent Seven? Z's likely not gonna stay given her JLD obligations, but you know how Morrison loves creating super teams in the hopes that someone might pick them up again. He did it with Cap Comet's team during his Action run, Seven Solders themselves, the Ultra-Marines being the heroes of the baby universe with no heroes, Justice Incarnate, and so on.
Plus, this Superman 100% fits the roaming cowboy motif. This is probably gonna be my guess till shown otherwise.
Edit: In fact, the idea of a hero (or heroes) coming to a small town to free it from oppression by teaching the people how to fight is literally the plot of Seven Samurai, and that's the movie that has quite a lot in common with Magnificent Seven. And funny enough there's 6 Dark Multiverse Superman characters being oppressed.
I'm changing my guess to the idea that roams the Dark Multiverse with his newly freed friends and counterparts righting wrongs and moving on like, again, cowboys or ronin samurai. Final guess. No take backs.