When the time comes hoarders will move their coins to other addresses with improved key schemes.
That was my thought. It won't be an "authority" that does this, it will be unscrupulous individuals who discover or gain access to the algorithms and use them to scan the blockchain for old enough addresses that still have coins, access those coins and transfer them to newer secure addresses in their own control.
Some will be "lost" coins, and some will belong to hoarders. As the problem accelerates, most hoarders who are aware of their bitcoin fortune will move their coins to more secure wallets. The paranoid increase their security with some regularity, and higher BTC value tends to increase paranoia.