He will probably use them to pay autonomous agents for big changes.
What kind of agents and big changes? Sounds ominous.
I'm not good in giving examples but let me try.
You see, autonomous agents with Artificial Intelligence will be making most of the important decisions in our world.
So, just to give an example, imagine an autonomous agent that can decide the type of questions lie detectors at airports will be making people. They could decide the percentage of questions that would be looking for:
A - Terrorists
B - Sex abusers
C - Drug dealers
D - Thieves
E - Assassins
The automous agent would then have five bitcoin addresses and would use the amount of received coins quotas to decide the percentage of each type of questions to be made.
This is just a very simple example and as I said I'm not good in it and I'm not particularly inspired.
But bearing in mind that AI agents will be deciding in all important matters in our world you get the idea. AI agents are driven by aims and objectives. if you can send coins to weight the components of such aims you get such scennario, where anyone could spend coins to determine the probability of an outcome.
Another thing could be advertsing. Satoshi could spend his coins to promote a cause. And stay anonymous.