Interesting hypothesis, but these could have also happened...
- He lost the keys (James Caan doesn't know how to do backups)
- He became incapacitated in some way, and family/friends didn't know he was Satoshi, or how to recover the funds
- He saw how big Bitcoin's economy had become, and chose to destroy (or put on ice) his private keys, knowing that if the early blocks move it could crash the economy
Yes, almightyruler, anything could have happened. And Satoshi knew that all. He tested all the blockchain with more computers before releasing the applications. He knew what can happen.
Gavin Andresen started a project to give away free Bitcoins https://freebitcoins.appspot.com/ (no more working) and Satoshi wrote June 2010:
Excellent choice of a first project, nice work. I had planned to do this exact thing if someone else didn't do it https://bitcointalk.org/index.php?topic=183.msg1620#msg1620
He waited but thought that someone else will do it. We think that he is waiting that someone moves the early mined coins to show to the Bitcoin community that it's a prize competition and that the private keys are somehow on the blockchain.