I was hearing rumours that Wicked was going to be on Quantum before Mamma Mia was announced. I could see wicked working on board.
What it seems is they pick a "Tony Award" winning musical that has been established as a hit on the stage and then pick one of them. If they paid a high price for Mamma Mia then it might be on the Quantum Class across the board. The wife would like that.
I was on Oasis last year and enjoyed Hairspray. Also had a little personal gig from the main two stars with about 50 guests. Great fun. But if the shows are being moved around I would want a new ship like Anthem having Hairspray on it instead of a new show.
Maybe roll out the shows to other ships and but new shows on the big ships.