I think more will come of the Deb thing. I mean, Quinn is still suspicious of Dexter. And with Rita being killed in a Trinity manner, I think shit is just going to get all fucked up next season. Maybe Quinn is going to do something that will make Deb more suspicious of Dexter, and maybe she will find out herself.
I mean, she is becoming a pretty good detective. She found Trinity's identity even with Dexter trying to fuck things up the whole time. She solved the Lundy case. I wouldn't find it strange if the FBI took an interest in her next season, honestly.