They're only going to be able to manipulate the market if they actually buy into the market, and no just bet on the future of the market. And if the buy in then sure once they've bought in enough they'll be able to manipulate it. But for them to buy in that much the price will skyrocket.
This.
The only way they can manipulate the market down is to dump coins. To do this they'll need large reserves, which due to Bitcoin's scarcity will entail spending lots of money up front and driving up the price in the process. Net result: almost even. Meanwhile Bitcoins natural growth will keep marching on.
Squeezing shorts will be much easier. They'll simply buy with the vast amount of fiat currency they already have, also driving up the price. Only the rubes will lose money.
Remember, this isn't an ETF. It's a futures betting operation, a sort of casino. Their customers won't be investing, they'll be gambling. All bookies and casino operators expect their vigorish. They also decide on the spread or number of zeroes on the roulette wheel.
I see this as just an expanded form of Satoshi Dice, and we all know how much SD helped Bitcoin get through the early days when it was trying to establish itself beyond alpaca socks, overpriced pizza, and the Silk Road.
Every little shopkeeper, hooker and cabbie in Vegas benefits from the big casinos being there. I personally welcome the futures markets to Bitcoinland.