The migration to streaming platforms are going to be what will keep them alive. Movies are more likely going to get a theatrical release if they're going to be a big tentpole blockbuster and having exclusivity on your streaming platform (ie Paramount Plus, Amazon Prime) will get subscriptions.
Release windows from box office to home viewing are going to contract - instead of the usual 3 to 6 month wait for a movie, it will be about a month or even less.
The thing is too, production methods are changing as well. I was floored at how The Mandalorian's production was done on such a small scale. With the technology that is being invented and created during these conditions, they can compete with large scale blockbuster summer movies and not sacrifice any of the quality. I think more studios might take notes from Disney and start thinking more along the lines of a mini series like Loki, The Mandalorian, or what Apple TV is doing with Foundation or Ted Lasso to encourage subscriptions. It really isn't that far a leap, considering how movies are now being planned as being two, three or multiple parters (ie. Stephen King's It, The Hobbit movies, Dennis Villeneuves' upcoming adaptation of Dune, most young adult fodder like Hunger Games, Maze Runner and others) before they're even put into production.
Finally; piracy is going to make a huge comeback with all of this entertainment being available online. At some point people are not going to want to add another subscription fee to their credit card bill.