You also have no idea about what OpenCoin will choose to distribute the rest.
And OpenCoin knows exactly where and when they will distribute the rest, and are therefore in a position to play the market accordingly.
True, but, OpenCoin interest is aligned with all XRP holders. And the ripple market is also much more transparent than conventional markets. Anyone can watch the OpenCoin addresses (like we can watch Satoshi addresses). And everyone can see the amount of funds entering and leaving gateways. Compare this to the current bitcoin exchanges, where whales and exchange insiders have an exclusive knowledge of fund flows, and therefore a huge information edge.