Why would a water park have to cost $700 million? A major ProSlide installation runs about $5 million at most water parks from what I remember, and that's usually with other nearby improvements as well. Slides and attractions for a nice water park would probably run no more than $100 million for a very well populated park. You really think they'd have $600 million in other spending (not to mention I would expect anything less than 5 to 10 years old to be moved from Wet and Wild) on the rest of the park? I could see them making a pretty decent water park in the $300-500 million range.
Also, pretty much finished a basic Excel sheet of 39 total possible lot purchases, and even when I start adding in building and assessed values (I just used the market land value to start), the empty or "not so nice" lots over on Major Blvd. are really kind of small peanuts compared to the larger lots Universal used to own in the area south and east of Lockheed Martin. I'll go through and break down the lots into areas (Major Blvd., South End Development, etc.) and go back through and get the building values added to the Major Blvd. lots. But at first glance, I'd estimate the Major Blvd. lots to go for a combined price of about $35 million including adding building/assessed values to the land values I have. If you want to add another $15-25 million to some businesses to entice them to move, you're still not looking at too much above $50 million. However, that only gets you the "lower half" of Major Blvd. I doubt Double Tree would be willing to give up the location and business (and aren't they the main partner hotel for Universal?), and the newer development in the northern half seems pretty nice and probably too expensive to buy out. The Days Inn and visitors center are not exactly pleasant to look at, and losing Days Inn would not be a major loss in hotel rooms to the area count, especially after Cabana Bay opens. Hyatt Place and Holiday Inn may be harder and more expensive to buy out (their facilities seem in much better condition than the Days Inn, but Cabana Bay will more than cover the lose of these three hotels, 802 rooms total), but I would think its certainly possible if they have/are willing to throw a bit more cash that way.