The expected discounted value of all bitcoin's future cash flows is zero. This is because the only cash flow that a bitcoin investor can expect from an investment in bitcoins is the revenue from selling the bitcoins in the market... and the market value of something that has no use case and is held for speculative purposes only (i.e. has no intrinsic value) will tend to zero in the long run.
A fiat currency that is issued by the government has no intrinsic value either, but there's one crucial difference compared to a cryptocurrency: in the case of a government-issued fiat currency the central bank will intervene the market, by making use of its prerogative to conduct monetary policy, to ensure price of the currency doesn't drop to zero.