I can guarantee you that lost btc address will eventually be subject to forfeit much like an old bank account with no action gets grabbed.
An untouched btc address in terms of no funds ever removed will be considered lost .
The funds will be folded back into mining rewards for blocks.
There are some that think that this is CSW's motive behind BSV based on various things that he has said. I don't really see it happening with BTC but it's not impossible. There's also the possibility of quantum computing meaning that private keys will no longer secure and BTC will have to be moved to a more secure scheme or be swept by those with the capability.