I'm already seeing WPF being used more for quick internal applications, so at least developers are toying with it, but as it stands it's still hard to design WPF applications.
Having tried the (awful) WPF designers in both VS2008 and VS2010 it's no wonder adoption is so low. I also imagine the .NET 3 requirement doesn't help things either: XP users have a potential 350MB install requirement.
I see WPF now as being where ASP.NET was in the 1.1 days: shunned by the 'passionate' people because it's a lot of work to get it to do what you want it to (this was before Control Adapters and improved standards compliance). I imagine we'll see an update to WPF in VS2012 that makes WPF easier to work with, a kind of "WPF MVC"-style relaunch.