So, possible scenarios:
1. Satoshi is a group of people. Subscenario 1: Founded by some powerful entity, to create an experiment or destroy banking system. Or make drug trafficking easier.
2. Satoshi is dead. He didn't really knew that bitcoin might have such success, he died before seeing it growing so much and that's all.
Subcenario 1: Satoshi was killed because of Bitcoin.
3. Satoshi is affraid of Bitcoin and how it turned up.
4. Satoshi is a person that has no life other than programming (21.000.000% nerd) and he creates things under different identities. Maybe was behind Napster too.
5. Satoshi is ET or AI or GOD or S8TN
Ill go with number 1 and 5. Probably Satoshi is a group of people who made an AI for there ideas to become more successful. AIs are really tough to manage, they learn by their own capabilities and information. Probably Satoshi (as a group) did not know that their AI become so knowledgeable that it made them successful. Thats just probably what I think it would be.