Busch, SWO, and LEGOLAND don't quite target the same guests Disney does. Yes of course there is lots of spillover and these parks are always to take a day away from a Disney trip, but no one is booking trips and flying halfway across the world to go to Busch Gardens or LEGOLAND. Sea World, actually to a degree, is more of a destination park than the other two but still has its own audience.
Universal Orlando basically demoted themselves to this 2nd tier when Rank Group gave up on the resort after initial IOA's financial woes. Universal Orlando re-establishing itself as an undisputable tier 1/world class theme park will have a dramatic, long lasting, and very different impact on WDW's business than anything else that has come before.
When IOA opened in 1999, Disney had both RnRC and Test Track coming online in the very same year. RnRC was a direct and rapid response to IOA, the other ended up being a bit of a happy accident as Test Track's delays gave Epcot a serious edge when it needed it. Kali River Rapids also opened at DAK on the very same year, keeping that still brand new gate looking fresh against the new competition in IOA.
Things aren't the same in 2013, and they sure as hell won't be the same in 2015.
That's why this time it's different.