Reserve currencies are not infinite, they come and go. During the past 568 years, we saw 6 of them. The Portuguese real and the Dutch guilder have held the role for 75 years. The French franc for 105 years. And the British Pound sterling and the Spanish real for 110 years each (the longest period).
An average lifespan of a reserve currency is 95 years, and the U.S. dollar has been at it for 93 years now. So according to the stats, we have around two years to go until the end of an era. And at that point, bitcoin might as well be the currency that replaces it.