Well, yesterday I learned of something new. Acropolis. It's Microsoft's newest "toolkit for creating modular, business-focused Windows client applications" and it "enables you to build reusable, connectable components and assemble them into working applications that are easy to change."
At first glance, it's a replacement for CAB and some of SCSF, using WPF. The downloadable help file mentions WinForms, but also mentions that the current CTP only supports WPF. By the looks of it, it will never support WinForms, but that's just my guess.
Most, if not all, of the Acropolis concepts are the same as CAB, even some of the names are the same. It would appear that they combined commands and events into a single concept though. The WorkItem concept is now the Part concept. Modules seem to have gone the way of the dodo. Views are now Part Views, etc.
As I've said before, I will post more as I learn it.