*** SPOILER ALERT, do NOT read if you haven't seen the finale!!!***
(I don't know how to do a real spoiler, sorry
It doesn't make sense to me, because:
1) That guy who was chasing Hannah is going to wake up on the bus and remember everything that happened. Everyone is going to be wondering where Dexter's child went since learning of his 'death,' and that guy is going to tell them that he saw Hannah running off with him. A big search for her would start in Argentina since she kidnapped a child and there's no proof that that was Dexter's will.
2) I don't see how working as a lumberjack cures him of his need, or is a conclusion to his life. Wont he miss his son terribly? How can he resist killing, and looking for his son one day?
3) I don't buy Hannah raising the little boy at all. She hadn't been around nearly long enough, and she made her debut into this season by drugging the Morgans. I think she cared about Harrison, but I don't see her sacrificing the freedom she had to raise him alone.
4) The whole police force was never informed of Deb officially dying, and all they're going to find is everything unplugged and her body gone. Thatll turn into a mystery, and again, a search..