A quick drop of $2500 would probably cause 90% of the miners to shutdown as for most of us our costs are closer to $3500/BTC.   So block times would slow to around 90 minutes / block.   That would further increase the cost of mining short term.    While it possible some fork could be done to change the difficulty it would basically freeze most transactions for months.    The problem isn't really with the mining it is with the users and the press.

A slow decline to $2500 would be survivable, but BTC isn't prone to slow moves.   This would have to happen over months to allow the difficultly to adjust.  

Generally short positions cost money to hold open as one is playing interest.   Shorts generally don't survive for years.    Long positions just cost opportunities and one can often hold even for decades.  

(Currently 1 TH is running me around $0.11/day and most of that is the cost of electricity)