I think you're right about the next few years being tough on Disney in Orlando. They're having to adapt to competition in the market they've never dealt with before, and they're slow to turn the ship. One thing I'd hedge on though: I really don't think MK will see significant declines. As you said, MK is the benchmark, and I think that's the one park that everyone will continue to go to, regardless. I'd expect MK to continue to gain business as more people vacation in the Central Fl market, actually, but maybe not the large gains they have seen in the past. I don't think there will be a huge shift in pattern where people forgo Disney, I think Universal will gain days out of the Disney vacation. Some will switch their entire plan from only visiting Disney to only visiting Universal, but not the majority. It will take a while to really gain critical mass for people to look upon Universal as equal to the Vacation Kingdom.
Universal doesn't need to be seen as an equal to Walt Disney World. It just needs to be seen as better, and more importantly it needs to be seen as being a better value. This doesn't mean being cheap. It means delivering a better experience at a lower price than WDW. Universal is well equipped to do this. As Universal does this, their growth story writes itself and it will come from Disney losing every full freight, cash paying customer that is not tied down to DVC or free dining or some kind of irresistible loyalty to the Disney brand that is beyond trying to break.
MK will not be THE tentpole of an Orlando vacation in 2015. It will be a fixture of the Orlando vacation for sure, but it will not be the main reason people are coming to Florida. Proof of this is already in the pudding in California where DCA has lured a significant amount of daily attendance away from Disneyland since Cars Land was unveiled. Of course, in Anaheim this balancing out of the resort attendance was actually healthy as DCA is still dramatically growing DLR attendance as a whole. But it does serve as a clear example that as soon someone builds a theme park with new, relevant product that is perceived as just as high quality as a Magic Kingdom branded park, business can and will shift.