Bullion banks expect to make a profit... the massive short position allows them to control the markets... unless of course they get overwhelmed with buyers...
So the answer to your question is this... who knows what will happen? It is going to be very interesting for the next few weeks...
I should say, the lender is stuck only for losses above the margin when buying back the gold (which is usually in or owed to individual investor accounts when the lender is a brokerage) since the lender is holding the margin and principal.