I think theatres will slowly start to re-open if they can distance actors/crew and make a profit with a distanced audience. Some smaller shows are already returning. I think the bigger issues with theatre is entering and exiting in large groups, once seated the risk is probably lower. Also theatre goers are geneally sober and quiet.
But given the evidence of transmission from gatherings in pubs & house parties, I don't think we will see night clubs operating as full clubs with loud music etc for a long time. Its going to remain table gatherings only in the law I expect and we may even see more "lockdown" of pubs/bars if people can't be trusted to stick to their tables.
A majority of entertainers now-a-days don't work in theatres, they work in clubs/bars and private venues (birthday's weddings etc...)