Since the opening of Disney-MGM Studios in 1989 and Universal Studios in 1990, Universal has kept reasonably well-paced with WDW.
What Universal has failed to do is overcome Disney's initial advantage gained from its pre-Eisner theme parks, the Magic Kingdom and Epcot.
Until Universal creates a theme park to rival the Magic Kingdom (something nearly impossible to do), it will always play second fiddle to WDW.
What Universal potentially can do with a 3rd Gate is steal the "short vacation" market away from Disney. But Universal also needs the hotels, airport transportation, and pricing to beat Disney in the 3-to-5 day vacation market, a market that has been growing in the United States where vacations have been trending shorter.
To succeed, Universal needs to capture all of the vacation dollars from the time someone lands at MCO to the time they depart.