Lol I was thinking of the oracle being removed. Here is what Inno says the theatre will do:
Owning a theatre will passively reduce the duration of all celebrations by 20% and it will reduce the costs of the city festival to these values:12.000 Wood, 15.000 Stone, 12.000 Silver.(Mind that the Theatre Play as a standalone celebration will be removed due to this change)
I see no need for further discussion on this idea since they already plan to shorten it and reduce the costs.