Thinking about it more, I think there is a very good question re that will survive in musical theatre houses 200 years from now. How many musical have really survived from the 1930s?
We may want to say that before the 1940s doesn't count because so many were essentially revues before then, and that revues are simply not what most audiences want to see today, e.g., 5-6 years ago, After Midnight received great reviews, but could not find an audience. What is the likelihood that even today we are going to see revivals of any hit revues, except perhaps (God Forbid) Smoky Joe's Cafe or Rock of Ages? Tastes change. Who knows what is popular today will be reviled in 50 years, let along 200?
I think that it is possible that nothing will survive as traditional musical theatre still being presented in real theatres...not even sure how many songs will survive. Anyone wanna listen to a few madrigals or a medley of Stephen Foster songs?
200 years is a long time. If I had to put money on it, i would bet that the things most likely to survive will be those that are suitable to be performed for limited performances per season in opera houses, perhaps Show Boat, Sweeney Todd, A Little Night Music, The Most Happy Fella, Candide, maybe Les Mis, maybe Phantom, maybe 1776, maybe MFL, maybe Oklahoma, maybe Fiddler, and a few others. Definitely not a lot.
I doubt that any musical comedies will survive without totally new books and some songs eliminated, simply because they will become so dated. I will never actually know, but I would be shocked back to life if Hello Dolly or or The Producers or Mame (some of my all-time favorite shows) or How to Succeed or Little Me or Book of Mormon or A Funny Thing survive.
Of course, the other issues impacting real answers are more interesting to reflect upon:
-- Will there be a thriving planet in 200 years, per JBroadway's last sentence?
-- TV has changed theatergoing habits for good (think of how many more dramas and light comedies used to open in a season even into the 60s at least)?. How will the evolution of TV further impact theatregoing (and interest in seeing 200 year old musicals).
-- What opportunities are technology advances going to introduce? As an example, will live performances be available to view inexpensively and holographically from your home, will you ever have to go to a theatre to feel like you are really in a theatre seeing something live? What advances in Virtual Reality will occur. Who knows what impact those advances would have on incenting people to mine old treasures, especially if shows can be recreated relatively cheaply, e.g., by computers. This of course requires there to be audience interest.
-- How much free time will people have on their hands? The more free time, the higher possibility of old works being mined.
-- What will productions cost to open and run? Will old classics actually be revived with the expectation of running for 'reasonable durations' in live theatre performances and / or will much better versions of the TV performances over the past decade be available, again to the point where you really feel you are in a theatre and the performers are right there live?
-- What will tastes actually demand 200 years from now.
I am sure this sounds like pretentious twiddle, but just think of the impact of technology advances over the past 30 years alone. And think of all the subjects on this board opining on what shows have dated well, what shows are not politically correct, etc.