Not sure how long your "few hours" is but assuming that you want a transaction confirmed within 3 hours (according to bitcoinfees) you would need to drop a minimum of 301 satoshis/byte. Considering a hot wallet would need to spend multiple inputs, let us consider n average size of 522 bytes. That results in a fee of .00157122 BTC just for maintaining less than three hours.

But let's say that the average user withdrawal (given deposit sizes > withdrawal sizes) requires about 384 bytes. This is still .00115584 BTC and thus unless a user has wagered at least 100x that during their session, the casino would be operating at a statistical loss.