Drucci-
Spoilers.......
Quinns definitely going to know it was Dexter. Liddy told Quinn he was going to bust Dexter, then he turns up dead. Quinn also has pictures taken by Liddy of Dex and Lumen throwing the trash bags into the Ocean.....and they also kind of tipped you off on the previews for the finale when they're all at the crime scene and someone speculates what might have happened to Liddy and Dexter responds with a comment like "or maybe he was sticking his nose where it didnt belong" looking right at Quinn while he was saying it.
My personal prediction is, Quinn ends up doing nothing to Dexter, because after Dexter has now destroyed all video/audio surveillance Liddy took, all Quinn has left is circumstantial evidence. Not to mention that Dexters house was bugged with equipment signed out in his name, that there was no court order or search warrant for. So Quinn wont want to risk his job and his relationship with Debra over this Dexter theory that hes already gotten in trouble for.
I think Dexter tracks down Lumen and ends up having a big struggle with Jordan Chase. Quinn and Debra finally locate Chase, they walk in right when Chase is about to kill Dexter. Quinn shoots Chase and saves Dexter. This way, Dexter will back off any anger he has about Quinn over spying on him. Quinn will have saved Dexter and will be back in Debras good graces and they can have a relationship. While Dexter explains to Debra that Jordan Chase was trying to make his friend Lumen the next barrel girl and he was trying to save her. Thats my theory.
I just cant see Debra finding out about the serial killer in Dexter and the show being able to go on.
It's gonna be a great finale though, I'm psyched for it, and I'm glad theyre not showing a repeat next week and making us wait two weeks to see it.