WPF and Silverlight aren't dead in the same way MFC isn't dead - Microsoft added new features to WPF in VS2012 so nobody could say it is dead as such. It's just not being pushed by Microsoft any more and that's why there isn't lots of sessions on them at Build: because Build is essentially a marketing exercise - marketing technologies at developers.
If it was a training exercise then sessions would be based around technologies that matter to most working developers e.g. SQL Server, ASP.NET, etc. instead of the shiny new stuff MS wants developers to use.