This is correct, if we are seriously discussing 20 or 30 years 'retirement'     Either bitcoin will exist at that point and be used, have worth exchanged in various retail trades or it will be dust in the wind.

If BTC really is being used in 20 years its going to be worth a ton, 21 million vs billions of people, even if only 1% of those are using it makes that system of worth alot per coin.   1 bitcoin will be all you need, I concur :p