I'm guessing the thinking is that people bought coins specifically to invest with Pirate because of the high interest rate. Once they get them back, sell them and go buy some big boy toys.
The counter-argument would be that they would expect a panic sell (or at least recognize it if it happened) and so should be willing to wait a bit to sell as the market normalizes. So if Pirate does repay people, you would expect a significant medium-term downward pressure on the price of Bitcoins as more and more investors pick that time to cash out.