I agree with the people who have opined 'good luck on 2021 (or 2025)? These things are never completed on schedule.
Re one-person shows, I think Liza has already demonstrated on a number of occasions that the voice is no longer functioning. To do something like recreate her mother's show -- if I understood that suggestion correctly -- is almost cruel; except for Liza groupies, I fear that it would be an embarrassment for all concerned, including audiences. Barbra is a good idea in principle; but, if it is more like 2025, she will be on the verge of 80, and Bette not far behind. To me, therefore, neither makes sense.
Re predicting new musicals, it is far too early to know what will even be real in a couple of years from now, and that is what I think it should be, and definitely not the Sondheim musical, if it is ever produced. That sounds like the Ritz or Booth to me, and IMO it sounds like it won't have even the broad appeal Passion..
An overdue revival may be a realistic prediction today, and it should be a splashy show...how about Mame (with a huge star or, at least, the next Lansbury) or A Funny Thing (with a huge star) or Dreamgirls (NOT the London production...big and expensive) or some sort of (new) old fashioned revue, a la Sugar Babies, with big stars or prior-big stars overdue for a career renaissance. Maybe with a new score. That would sorta be appropriate for the newly reopened Palace.
That said, I think it would be a shame if they did not open with a new musical. Maybe the next LMM musical (can you imagine the expectations around that one!!!).