This is incorrect. Bitcoins will eventually all be moved. There is a limit on how many can be mined. At that point, the "miners" will no longer be finding new Bitcoins, but harvesting the transaction fees (which take computational power to verify)
And by the final saturation point the value should be known well enough (and the other infrastructure aspects I mentioned will be in place) that lost coins will be a negligible concern. An expansion of "exchanges" will help a lot as then you no longer have problems with abandoned wallets as the funds themselves can be used elsewhere until the owner decides to withdraw.