My answer is a swift & painful drop to zero.

In a MarketWatch column, I wrote last May-June, I thought what it would take for bitcoin to become worthless. Bitcoin is getting close to that point. once Bitcoin’s price falls below its cost of mining, the incentive to mine will deteriorate, thrusting bitcoin into a death spiral. Because the ledger that maintains the records of who owns what — bitcoin is, after all, a set of encrypted numbers that cannot establish the ownership of anything — bitcoin will become worthless.