Thea as Speedy is going to happen. Roy is either going to be killed or go straight into Arsenal.
Sara is going to die. Laurel is going to be Black Canary but maybe not this season.
Malcom Merlyn is going to fight Deathstroke. He's going to come back to town because of Moira's death. He's going to fight Deathstroke because Deathstroke is going to go after Thea. This might mean she gets her initial training from Malcom for Speedy.
Arrow is going to be injected with the mirakuru to fix his knee and fight Deathstroke.
The cure for the mirakuru will be introduced and everyone will get cured.
Mirakuru is the substance of the Lazarus Pitt and the League of Shadows uses it.