I have heard a thousand times that many bitcoins are lost due to the owners either forget their private keys, lost the hard drive, or simply die before they tell their family about the wealth. Although 21 million sounds like a lot, but with accidents like those keep happening, it's sooner or later bitcoin will gradually...be depleted. I know now the reward for miners are new issued bitcoins plus transaction fees, could it be possible that some day the reward includes a new feature, that all wallets will give a small portion of its balance to the miners, either a small percentage of the balance, or just a few Satoshis per wallet. So that "dead" bitcoins will slowly become global wealth for all humans again over a great span of time? What do you think? Is it a very stupid idea?
First of all, this would mean that the new "protocol" would replenish the coin base from .. private properties. People will certainly not like this.
Second, in order to do this, there will have to be generated proper transactions that spend that money from the existing wallets, sending it to.. the holy wallet that puts money back into circulation.
As you probably know, a transaction has to be signed in order to happen. For this you need the private key, only the owners have. Will the owners do this themselves? No. Now maybe the wallet can do this, since the private key is saved there, right? Well, it has to be running. And as soon as one wallet will do this, people will use another wallet. End of story.