After the virus has been defeated, I won't go to casino immediately, I will take some time, cause Im not a gambling addict. So, I've decided that I will go for a short tour after the quarantine period, cause really, Im very tired for this quarantine. 
I think casinos will do it by default. Enough time will be spent closed to explicitly exclude the possibility of infection of the premises.
Although it is impossible to say unequivocally that all casinos will do this, because every day of isolation they lose profit.
When we say defeat, we are talking that the cure is already invented and there is a vaccine available that time already.
Therefore, there is no risk anymore so we can go anywhere we go, even in a casino, and that would also mean that our life will be back to normal.
However, if we are talking about the quarantine is over and casino can operate but with social distancing, then I guess people will think wisely before going to a casino since the threat is still out their and personally I won't enjoy gambling in a casino wearing mask or social distancing.