Live out a happy life, I suppose. Would probably diversify investment into a variety of things and otherwise sit on a stack of Bitcoins. If Bitcoin were to soar to something like that, it seems almost inevitable that it would have to be a practical currency that could be used for virtually anything, so actually, "cashing out", would probably be meaningless--I mean really, why would you cash out to dollars (which are guaranteed to lose value over time) when you already have a spendable store of value that has proven itself a million-fold

...Unless the reason Bitcoin is worth $1M is because the dollar has become completely worthless. In that case I'd probably end up dying in some war or another sparked by the global instability caused by the financially insolvent (but heavily armed) United States.