A very optimistic exchange rate could be estimated by assuming parity between the "market capitalization" of BTC and XRP. If 21 million BTC have a market cap of $600 million as at present, then 100 billion XRP might have a similar market cap. This would value each XRP at $0.006.
This has probably been answered many times over, but doesn't this make the developers (or whoever has the power to issue XRP)
incredibly rich and powerful?
Let me get a calculator...