It's not hard to see what that demand is - for usable, provably scarce currency free of politics or other manipulation by a cabal controlling it.
I am dubious the US dollar will exist in 20 years, or even in 10 years at the rate things are going lately. I'm very confident Bitcoin will be around as it continues to develop and improve with its army of developers. As I always tell people, don't switch from USD to bitcoin out of greed. Do it out of fear. The dollar is going to 0.
However, the ONLY thing that has passed the test of times as real money, is the only real money we've ever had, and that is PMs. Gold for wealth preservation, and silver for more practical uses.