I like to think DB Cooper made it successfully to a tropical Caribbean Island with the loot, whereby he enjoyed the fruits of his ill-gotten spoils and loved every minute of it, relishing the fact that he got away successfully with the most incredible hijacking and robbery in the history of the world, and defeated the efforts of every crime-fighting organisation in America to find him.
The only problem is, he couldn't tell anybody - but being the secretive guy he was, I have little doubt he relished keeping that secret as well.