Acropolis - The end
The Acropolis team just announced today that Acropolis will not advance from CTP to a supported release. They also announced that they want to help customers who'd like to take Acropolis into production be successful until an alternative is available.
The good news is that all the great work the Acropolis team did will be rolled out in the future versions of .NET and also used for guidance and best practices for building WPF Composite Clients.