Since the writers have demonstrated that they possess all the subtlety of a hand grenade, I'm assuming that everything will be fairly straightforward. Which means Barry will get darker, but not a full blown snap to villain. I predict his father's death will cause the traditional superhero crisis of faith and he'll start sliding towards believing the ends justify the means to stop Zoom, he goes to Earth 2 to fight Zoom and something Barry does during the fight is what causes Earth 2 to start getting ripped apart, then he realizes he's turning into Jay and snaps back to being a hero in time to save Earth 2.