Yes. Bitcoins don't lose validity as long as you keep the private keys safe.
But it is quite possible that some of the huge bitcoin stashes from early mining are inaccessible due to lost wallets - people did not be particularly careful with their wallets when bitcoins were worth basically nothing.
Onkel Paul
Ive actually read that over 4million bitcoins have been lost. There is an industry developing of people going into scrap yards and collecting hard drives and checking if they contain any bitcoin which I find interesting. I think this will only increase as the price increases as well considering there are potentially 4 million out there