I think everyone dies, but I don't think they let Hanna 'win'.
My call from left field who brings everyone down?
Masuka.
The TRUE creep motherfucker has known what's going on the entire time, and it will be revealed in a slowly-unraveled set of flashbacks how he's been pulling strings and helping to cover Dexter's tracks the entire time.
He then ends up destroying everyone and everything, and takes Dexter's place as the Bay Harbor Butcher once his role starts getting exposed.
Think about it. He's fucked up, he's been very close to the whole thing (the arm is one example), he's got same level access as Dexter, and he's also totally awesome.