If they really hold that many BTC and their Form S-1 gets declined then they might sell their BTC and the price goes down to less than $40 per BTC...
If they really own 1% of all bitcoins, they would wipe out the order book completely if they tried to sell. It would be stupid for them to try to even liquidate a fraction of it - the price drop on their remaining coins would erase any sale profit by an order of magnitude. Whatever you think of the Winklevii, they have more skin in this game than anyone and have no choice but to try and make Bitcoin a wild success.