I would be pleased to see live theatre return in some form spring/summer 2021, but even if a vaccine is widely available by then, I don't see some pre-pandemic practices returning, which is fine by me.
The stage door, for one, has met its Waterloo. When crowded, tightly cramped spaces (especially for the shows appealing to younger people and those with big stars) combine with the toxicity and selfishness of the fans, it gets on my nerves- as well as many others'- quite easily. In the end, it's up to the actors if they want to continue this, but I hope virtual programs like Cameo (hopefully they will be free though) will be the way of the future for meeting theatre figures.
More organized entrances/exits and bathroom lines will also be something to watch post-vaccine. Intermissions, if plausible, could be extended, as could the times theatre doors open to the public for every performance. Temp checks, keeping some sort of distance, and perhaps mask wearing will likely be here to stay.
“I am furious, but I am sailing.”