Do you think legal operations will close their doors and move underground?
If they do so, they will cut out a big piece of their revenues and throw it away.
Do you think it will only have a limited impact on Crypto currency prices?
Yes. Why are you thinking about adverse effects only?
Crypto is meant about anonymity and privacy, so crypto like XMR, Dash and other privacy-pegged coins will be used more because gambling is an addiction and nobody can prove this statement to be false. So who can save those gamblers, the real gamblers from gambling?
Will these operations move to countries that allow online gambling?
Quite possible because if they have alternatives nearby, why would they lose on their share of the revenue they are already getting in their field?
Will online gambling evolve into illegal sites on the Darkweb?
Yes, as I said before, there is a high possibility of gambling turning illegal at places where it will not be allowed so not to leave their customers in vain.