[niij]

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)

[CmdrSprinkles]

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.