I doubt they wish they'd done that. HP has driven huge increases to the visitor numbers to both parks, which before HP1, some thought were getting a little state. IoA has basically doubled it attendance figues since it opened. The other issue is where would they have put a separate park......things have changed a little now as they have earned so much money from it. Not to mention the addition of Simpsons land, Rip Ride Rocket, Transformers etc with a number of big developments to follow behind, things have never looked so good for Universal, the two park split of HP even allowed them an massive up-sell attraction in the Hogwarts Express....how many people are going to miss that for the sake of buying a multipark pass?