Influence IGMarkets on BTC price

Hey Guys,

A couple of days ago a friend received an e-mail from IGMarkets that future trading in BTC will stop from 8th November until further notice because of the upcoming fork(s).

Yesterday, 8th november, there was a BTC 'dump' what created a marketcap fall of 8 billion. Could it the possible that the ending of BTC-future trading on IGMarkets have started this fall? As far as I know, please correct me if i'm wrong, IGmarkets needs to buy a (real)BTC for every BTC-future that is traded on their platform. Because the trade is closed it would be no use to hold the BTC they bought as deposit and they dumped them on the market.

The reason for this question is to 'guess' the impact of new brokers starting offering BTC-futures in the future (like CME and Chase). How large will their influence be regarding the BTC price when they need to buy and hold BTC for every future that's traded on their platform (assuming that the trade will be continuously and therefor the hold on BTC also)?

Thanks in advance,

Cheers!