What do you think happened in the ending?

Either Ben died or he lived.

I am on the side that he lived. Remember that he pretty much dove straight down below the plane. Something that Hope knew and undoubtedly told Ryn. If he was dead then Ryn would have been able to find the body.

I think that Ben somehow achieved a transformation, or at the very least is still in the water trying to see how long his body can be there.

Plus when we see him floating in the water we dont see any blood.

I think that him surviving would have been revealed in season 4