Bitfinex should negotiate with hacker. Offer $10 million to return the stolen bitcoins and drop investigation.
this is so unrealistic...you think, that some hacker will accept risk of disclosure and less money, than stay behind with all money?
money, bitcoins, funds...whatever are already lost and there is literally no way how to get them back. if somebody to smart enough to perform this kind of "job", he is also aware, how to act right after...