I don't think this has to do with going back in time to eliminate the murder (if it was, they are making Cain pretty likeable for that plot twist) but maybe somehow having Abel come forward in time. I also think that Cain just dying isn't in the cards - he would just spend eternity in hell instead of on Earth. BUT - remember the statement in the story arc where Chloe almost died from Season 2 that (1) people commit themselves to hell, not Lucifer and that (2) there is a way out of hell - that's been in at least two story arcs - must be a reason for that.
Also, I am surprised at the negativity about this episode. it wasn't quite as good as the previous show but IMO as good as most Season 2 shows