While I doubt Disney execs are pooping themselves when thinking about short-term effects of Potter on Universal, they'd have to be idiots to not look around at how well-themed that part of IoA is, and realize they need to step up their game. I'm not talking about anything as far-fetched as Uni becoming the premiere vacation destination in Orlando. But they now have some serious bragging rights. I don't know maybe I'm alone in this way of thinking, but here it is: I love going to WDW. Despite being a cynical sarcastic S.O.B., I can go to the World and be a total sucker for the "magic" shpiel. I'm a DVC member, I always stay on property, blah blah blah. But I think a lot of Uni's and IoA's attractions blow WDW out of the water. And the hell of it is, it's my combination of love for WDW and the way WDW kinda screws its guests by raising prices so much higher than the rate of inflation, that keeps me from going to Uni more often. I only have so much money, my lodging is paid for at WDW, and MYW pricing makes it more affordable to just do things onsite. That, and my wife likes to relax on vacation ONCE in a while, which we did not do when we also went to Uni.
Now, to a degree, WDW doesn't mind my way of thinking. I think Uni's better, BUT I spend far more time and money at WDW. It's a tradeoff they can live with, I'm sure. But sooner or later, if enough people share a similar way of thinking, it's going to bite the Mouse on the tail. I'm not saying WDW's ever going to have a "Going Out of Business" sale, but I am saying that they're in danger of losing their theme park mojo. First, people will start comparing Uni more favorably to WDW and then maybe, just maybe, a subtle shift will occur which actually affects WDW's bottom line. Time will tell, as will Star Tours 2.0 and the Fantasyland expansion. But if people start to think the true innovation is happening at Uni, it's going to mean people spending more than just one or two days of their WDW-based vacation at Uni. You may start seeing a more-even split, especially if Uni starts developing more to do, and more onsite amenities at their branded hotels.
*I'M* not worried about it. But WDW should be, at least to some degree.