I think a longer run would be lovely. My friend group is already talking about a repeat visit. A-listers want to be in this show and I have to wonder if it isn't a little easier (and maybe cheaper) to put people into the show since it's really a staged concert.
Also, something some non-theatre friends said recently after seeing the show--"what I was really struck by is how fun and entertaining and popular (based on audience reaction) this show is, but at the same time how much the writing, the music, the piece itself, is such a cut above most everything else I've seen recently". I think it's striking a chord with audiences because it is deeply satisfying artistically, but also fun and accessible (a balance most Sondheim shows do not have--nor would I wish any of them to be something they are not, I love them all).
I only mention this because I think this balance is one of the reason the revivial could play longer than just a few months, and why so many want to be a part of it.