I believe this guy knows what he's talking about:
Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone.
satoshi is a person from the future, he/she has even predicted in great detail that the missing coins will be a donation for everyone.
IMO, Satoshi didn't predict it. If you checked again why he made that statement, he was trying to respond
virtualcoin's post at that time. And I am sure Satoshi was aware of the possibility of losing Bitcoins on the wallets because of hacking, forgetting wallet passwords/security keys/private keys, or other problems.