There would be a dual market, futures and Bitcoin market, might be interdependent or independent. Cash-settled Bitcoin futures would allow Bitcoin skeptics/institutional investors to bet against Bitcoin without even buying it or there is a possibility that these investors will want to suppress the price so they can buy Bitcoin at a discount, either way this would lead to a new price discovery mechanism.
Just read an article on, will the futures market do to Bitcoin what it did to gold?
1: The velocity of information is orders of magnitude faster I doubt most market participants in 1975 even knew that gold futures were a thing.
2: The Demand to hold Bitcoin is one of the highest of any assets ever Bitcoiners have learned to buy the dip and hodl.
3: Bitcoin has more competitors than gold.
https://medium.com/swlh/will-the-futures-market-do-to-bitcoin-what-it-did-to-gold-b7d35704641