I have been thinking about this a lot recently. The question I am asking is how much effect exactly will futures trading have?
Evil whales sell paper-BTC on the Futures market creating a discount compared to the price on the physical-BTC exchanges. They can do this until the cows come home because it then needs Arbitrageurs who will sell their physical-BTC to buy the paper-BTC and pocket the difference as profit. This is where the actual selling pressure on exchanges would come from. Basically HODLers who are willing to sell out physical for paper BTC.
The thing to watch will be the price comparison between physical and paper BTC to see if they are really going to be able to use futures to Wag The Dog.