Bitcoin’s early growth was driven by capital-base asymmetry, engineered scarcity, and reflexive adoption. As issuance declines over coming decades, the network transitions from a subsidy-supported growth phase to a maturity phase where security must be sustained by fee demand, price stability, or structural evolution. By 2040, Bitcoin’s long-term security budget becomes the central economic test. The article explores three potential equilibria: a fee-dominant sovereign settlement layer, convergence with gold as a reserve anchor, or perpetual issuance models such as tail emission — while acknowledging the political constraints around altering Bitcoin’s monetary design.