It will still not lose, since it'd be as if the double spent ones had never happened. They do stop winning, but never lose
Really? I don't know how Casinos actually work but losing profit is actually a loss, value isn't being created out of thin air.
Replace the Casino example with an exchange.
Bitcoin price = $1000
I deposit 1
BTC, the market crashes, and I sell it for 100 USD right before the market shoots back to $1000, I then go and double-pend that 1
BTC, the exchange will freeze that remaining $100 but that does not solve their problem, the person who bought my 1
BTC will want to withdraw it, in this case, the exchange lost 0.9
BTC which they need to pay to whoever the person that bought my "imaginary" 1
BTC which was never actually confirmed in the exchange's wallet.
Also for a Casino, the double-spent amount is a loss they have to bear, the inner working of any casino or any organization for that matter does not matter, when someone double-spends something, someone else loses it, unless that someone lives in a vacuum.