As far as burning Satoshi's coins, the topic is highly controversial, as such it'll most definitely cause a fork. It's best to leave such things in incompetent hands of Faketoshi. Let him fork the chain once again unlocking Satoshis coins to himself. That should be his last battle after which he'll become a footnote in bitcoins history.
All bitcoins that are not moved for a certain period of time (20, 50, or 100 years) should be presumed lost and then recycled through the usual mining process. I'm not sure if that can be achieved through a soft fork.
I certainly hope not. This is a terrible idea. This is bitcoin not Ethereum