This article in the New York Post says that the Young Frankenstein musical can be considered a "flop" and that it may vacate its theater sooner than some are admitting to make way for the forthcoming Spider-Man musical. (Thanks to James H. Burns for the link.)
Speaking as an utter layman and outsider here: I liked Young Frankenstein and think it's paying a certain price for the overhype. Its ticket prices and promotion have grown humbler. I would also hope they still don't have so many people in the lobby being quite so pushy about selling you t-shirts and other souvenirs. (I really think that harmed the show a bit for some folks. It did for me. Made it feel like you were filing in to a ride at Disneyland, not a Broadway musical.) I assume they haven't changed a few of the musical numbers that ended with a soft thud but there's still enough in there that you can leave humming something.
But I don't know the math on this kind of thing and it may well be in trouble. If so, I wonder what this means for the future of the show. The New York production is so expensive and elaborate, I can't imagine any regional theater ever mounting a comparable production. That might be a good thing because in some ways, the show is diminished by its size. I actually think the show could lose its rough edges if its creative team — or others they empowered — did some more work on it.
Alan Jay Lerner once wrote that the reason Camelot was not as fine a show as he wanted it to be was that they had too large an advance sale. Coming as it did from the same crew that had just done My Fair Lady, the show could not delay its New York opening long enough to fix all that needed fixing. They'd sold too many tickets for the Broadway run. Also, the show was so costly with its lush sets and costumes that it was difficult to rewrite and in many ways a prisoner of its technical needs. They actually wound up making some significant changes, including cutting two songs, several months after the show had begun playing in New York.
That almost never happens. If a show is changed after it opens on Broadway, it's usually only to scale back its budget, not to improve things. I don't think they've done either with Young Frankenstein. Maybe they could.