If they don't pay him out then they're effectively finished here.
They have a choice - pay him the 84 bitcoin & continue running a trusted site & make profits for an unlimited time
Or
Scam him & pretty much end their business with a destroyed reputation over 84 bitcoin.
For the above reason I'm confident they'll pay him out.
They have paid over 100 btc before to a user so what makes you think he wont be paid? It has been said that fortunejack will be checking his win and after 10 working days if his winning is legit then he will get his withdrawal, all he has to do is wait since I believe he won that without any fraud