Let's see if Prism can go where Acropolis couldn't (yes, I know, they have different objectives). From Prism's site:
"Prism" is a set of assets for developing Composite WPF applications. "Prism" includes a reference implementation, reusable library code and pattern guidance.
"Prism" addresses the challenges around building complex enterprise WPF applications. As the complexity increases and the teams grow, the application becomes increasingly difficult to maintain. Using "Prism" enables designing a composite application that is composed of many discrete, loosely coupled modules. These modules can be developed, tested and deployed by separate teams.