The Short Version
This claim is false. The US dollar holds roughly 58% of global foreign exchange reserves, while no central bank currently holds Bitcoin as reserves. No credible, independent expert consensus supports the expectation that Bitcoin will surpass the dollar as the world's primary reserve currency. The most optimistic pro-Bitcoin analysis (from a crypto exchange) only suggests a conditional "earliest plausible window" of 2046 — contingent on multiple unmet conditions — which is a speculative scenario, not a mainstream expectation.