The Dream thing is likely. He does shoot himself up with animal tranquilizer, and seemingly show now effect. I wouldn't be completely satisfied with that, however. At least, not to the climax of a season. If it were midseason, or something, I would accept that.

That seems all too possible, though.

Then again, I'm thinking now more in the possibility of Debra finding out. Not immediately arresting him. Something bad happening to her. Finishing off with Dexter saving her somehow. Debra would however have to somehow lose her chief of police position in order for it to keep sane in that case, though.

Unless they're willing to have Debra die early on in the next season. If a third party were to find out, he or she could kill Debra in order to save Dexter. Maybe Masuka's nerdy assistant. Either he's a useless throwaway character, or he's going that way anyway.

Honestly, I hope they decide to use the next couple of seasons to wrap it up. They're better writers than I could imagine being, but they've had to have written themselves into a corner here, and the show might end up choking itself on it's own branches.

Either:

A) They completely destroy the dynamic of the show.

B) They reveal it's a hallucination or something that completely destroys the impact. Making them look afraid to take a risk.

C) Very VERY meticulously carefully plot this thing to work right.