Yep. Dead, lost access or in prison. I'm leaning towards dead.

Why is being dead a convincing idea? How old do you think he is/was, and why would it be likely that he would die? When do you think he died? The idea that he died doesn't explain how he came out of hiding twice.

Losing access by intentionally deleting the keys? That agrees with my point that he knows it would cause problems to spend them, and decided not to spend them.

Losing access by accidentally deleting the keys? Would Satoshi really be that careless?

I replied to those options here: https://news.ycombinator.com/item?id=47711594