Why do you think it will be approved? It all sounds very dodgy.
Basically, they are going to sell the ETF (initially at least) based on their own holdings of BTC, as the market is so unregulated and illiquid. If they were to sell their BTC, it would be expected to have a massive market impact, as the BTC market is so small and illiquid. So the whole principle relies on investors buying the ETF at a price which is higher than what Winklevoss would be able sell the coins at themselves.
Basically, they are asking for permission to sell something to investors at above its real price, on the basis that the investors are too stupid to realise this.
I don't work for SEC, but if I did, I fear my hand would be hovering over the 'Reject' stamp.