I guess, never.
Bitcoin has price because someone is willing to pay for it. Right now, because its price is going up, and Bitcoin is in short supply, people are willing to pay much money for it. And the ever-increasing demand for Bitcoin will keep driving the price up until people don't want to buy or hold it anymore. Would some one like to buy BTC for $100,000? Just to get $100,100 lately?
At that point, by the way, unless Bitcoin has become widely accepted as a legal means of exchange (as "money"), the price of BTC will collapse someday.