The shares won't "plummet" per se. They will most likely drop, of course. New questions will be raised in the business press regarding JCP's chances for survival. The financials will be called into question. The Macy's/Martha/JCP suit still has to be resolved. And, JCP's credit ratings will erode even further.
In the meantime, JCP has desperately sought an infusion of cash and, apparently, will use some of the GS loan to pay off older debt, fund operations, etc. The company continues to survive on borrowed time and borrowed money.
The critical question following the May 13th announcement will be, and continues to be: "What plans does JCP have for bringing back the customer base?" Without sufficient sales revenue, JCP may be forced to downsize...close stores, layoff more employees, etc. They have pretty much committed everything they have as collateral against outstanding loans. Ullman has no room to maneuver and no room for error in the next nine months.
Not likely more possible that they slipped out the back door with the bags of loot or are enjoying short positions after hedging into the run. In the end they will possibly own the real estate along with a whole lot of cash made along the way.