Absolutely. For instance, for the original production of NINE, the national touring set had to be redesigned to travel. The location was changed from a spa to a train station. Sometimes, changes that work on a tour are then reverse implemented into the Broadway company. If The Addams Family receives scathing reviews and producers and creative staff aren't sure the show will have legs, they can make changes after the show opens. When "Baby" was in previews in 1984, they did a massive overhaul. I saw the show four times, two in previews, two after it opened. They cut the narrator role to nothing ... only voice over and one brief solo. They cut Beth Fowler's song, "Patterns". It made her ineligible for a Tony award; the song has been added to every subsequent production of "Baby". So, yes ... change happens to shows after they open.