If from a developer's viewpoint, XAML looks identical to Silverlight, and there are the same number of people working on XAML for the Windows team as there used to be working on Silverlight for DevDiv, does it matter?

But I bet you're feeling betrayed. I understand. I felt a little betrayed a few frameworks ago. Post-betrayal, I stick to focusing on transferable skills and JIT learn the rest of .NET. I'm on a WPF project now, have not studied WPF deeply.

My advice: if you have any say in the matter, try to work with ASP.NET MVC as opposed to the .NET alternatives, so your skills transfer.

Footnote: I don't know how many worked on Silverlight/WPF/WP7 versus how many work on XAML now. I assume XAML will march on. But no one will care unless/until the Windows tablet is successful.