I can't imagine him being a single person. If he/she is, must be the Newton of our age.
The nice thing is that maybe 10-20 years from now, when Bitcoin will be used in all major institutions as a world wide currency, he can get out and tell us his (or their) story, and he will be able to prove he is who he claims to be because he can sign a message with the key used to create the genesis block.