Disruptive forces don't come along all that often in the development world. They do in the IT world in general. You could easily say that cloud computing or the emergence of mobile applications have been disruptive forces, but they don't fundamentally change the way we approach the task of actually writing code and developing our apps.
In the Java ecosystem, the last major disruptive force that really changed how we developed our applications was Rod Johnson and his promotion of dependency injection. The Spring framework really did become a disruptive force in the Java world, and even when DI and AOP techniques became more and more mainstream, Rod Johnson always remained a strong personality in the Java realm.
But what will be the next, big disruptive force in the development world? Is is Scala? Scala's got a good shot at making it. It's certainly got a passionate development community behind it. But what will it take for Scala to go beyond the tipping point as the Spring framework did at some point in the last decade? Maybe TypeSafe just needs more money to make it happen?