Opening the casino is just a small part in the overall equation.
I think the main obstacle now is the border control for both Spore and M'sia and what quarantine measures are required.
As long as you need to quarantine yourself before/after the trip and/or pay for the cost, very few would bother to go Genting (or for that matter anywhere in M'sia) for the moment.
So things need to stabilise to an extent that both govt is comfortable with doing away with quarantine/testing before most would consider travelling again.
That's unlikely to happen soon.