OpenCoin doesn't "control" XRP in the sense that they can just send commands to the network to create new ones or arbitrarily adjust anyone's account balance. There's no transaction that means "create XRP." Even if you were to add such functionality yourself, you would have to convince everyone else running a validator that they should accept your change. And who would authorize the creation? No one would accept it.
Instead, I believe they constructed a ledger by hand that holds a 100 billion XRP balance in a designated account. Then they ran Ripple off of this ledger. If you query the validators and go back in history I believe you can trace all of the XRP in existence to that one account (it's mentioned in the wiki).
Anyone could of course fork Ripple once it's open sourced and make a brand new ledger but then the problem remains, who gets the 100 billion XRP? It makes the most sense for it to go to the people that wrote the software since they are the best positioned to keep improving it (and they already intimately know how it works).
You could try to remove the XRP entirely but that will create an enormous number of new problems such as what to do about connection spamming. It's easy to casually propose alternatives but they are difficult to get working right.
Ultimately any scheme to change either XRP's creation or distribution will likely fail, because there is already a growing body of businesses that are conducting commerce with the existing ledger chain.
Ah right. Makes sense. This might be an advantage then because it would be more difficult to use a bug to mint coin than it would be to do so in something like BitCoin which allows minting.