I think they are done for good, and I wouldn't be surprised to see another service start up and take their place. Nicehash wasn't the most user friendly from the buying perspective. About the only thing it had going for it was that it made it extremely easy for miners. People seem to only be thinking about the miners who got fucked. But I am guessing the big time hashrate buyers had quite a bit of bitcoin in their nicehash wallet for purchases. Who knows what happened exactly but I am willing to bet whomever is responsible had inside access. No company would be that stupid to keep so many bitcoins in a hot wallet.
Exactly, much more had to be in the wallet of the buyer. And I would not be surprised if it launched a new competitive service next week.