There is more satoshi than atoms on earth. :)
The system is immutable. No one can steal your coins... In your lifetime.
But the goal of a currency is to be usable. If the currency's supply goes below 1 BTC, this will be a concern because this means that there is 21 bits (zeros) in every BTC price that are wasted. Pure storage space and bandwidth wasted. I don't think asking for a single transaction in a lifetime for the every coins is a concern.
So in 500 years we will have another forkening, between the believers of the classic Bitcoin chain and those who believe the old bitcoins should be recycled by forking. Oh god.. will this never end?!