I guess that Binance would decide to repay them from their own pocket and most of Binance traders my decide to stay at this exchange. Well, any exchange may be hacked so even if you change your exchange you would still have all chances to get hacked.
But at the same time remains the chance that people would decide to leave it. For example poloniex earlier was one of the top exchanges but later they had some issues so later they couldn't bring all traders back.