I'm mostly puzzled by the fact that someone would let $1 billion sit in a wallet without earning interest...
I speculate that in the future, Bitcoin might become valued so highly, that people don't even bother using it in favor of other coins, and as people don't use it, no one then accepts it, then it loses value, and by then people are accustomed to using other coins, and Bitcoin dies. Who knows, I probably won't live long enough to see it.