Deb could kill him to protect Dexter. Lumen too. RoboCop could get into a dispute with Quinn and they kill each other which would also ensure Dexter's secret. Or maybe Lumen and Quinn kill each other.
I really hope it's not the third option, that would be way too contrived. And I'd rather Lumen not be involved either - that would just be a repeat of Lila and Doakes. If Quinn's gonna die, it has to either be at the hands of Dex or Deb to really mean anything.
I can't see Quinn becoming an 'ally' per se. The only plausible way I can see him learning Dex's secret but keeping it quiet is if this relationship between him and Deb really takes off, and he stays quiet to protect her. But I hope that's not the case either - it's a bit too mushy.
I'd still like to see Lumen survive the season and move on with her life. I expect things will get crazy before it gets to that point though. Can't believe there's only 4 episodes left - it feels like we're only halfway at most. Too much filler in the first half of the season perhaps?
Also, am I just not paying attention, or is this two weeks in a row now with no James Remar/Harry?