I think putting Harry Potter in IOA is better than in a third gate, because when it was announced in 2007, Universal wasn't in a good economic position, considering that fact that GE and Blackistone never finacially helped Uni the way Comcast has. They needed a product in their current parks that could one day help them create a third gate, if that is their goal. The point is you must improve your product before expanding it. Disney did that in America before moving internationally, and so did Universal. The only problem for Uni, if this was their problem, is that you already used HP, and now they need to figure out how to fill the void to create a successful theme park. So instead of pushing the limits to bankruptcy to build a new theme park, they added Potter in IOA, and everything has worked to perfection.
Now I'm not as knowledgeable as most of you on this fourm so I could be drastically wrong, but I think the point is true. Enhance before expand. A third gate wouldn't hurt UOR, but they need the right place, right time to build it.