If Satoshi wanted to explain himself, he would have done it by now. But I don't think you will. Maybe at a very late date, maybe a letter will come out after he dies. I think this mystery is good. It's becoming more attractive.
Well I hope that letter won't reveal his keys to the wallet.
It would be best for him to just keep himself even after he died because the people will have more to investigate when people finds out who he is and his relatives like brothers or sisters. The media won't let them sleep at night if he left a letter. This letter or revealing himself won't help.