Thanks for your feedback. I will copy this as a work-item, so all the prism team will be notified about this. In addition, other users with the same interests could vote this.
First of all, take into account that there are not intentions in providing less WPF than Silverlight support in Prism v4. Even more, in Prism one of the main design concepts is Multi-Targeting which is meant to
provide guidance for the both platforms using the same code-base. For more information about this, you could take a look at the following documentation section on MSDN:
Regarding to the ChildWindow, in some quickstarts there are some assets that are specifically created for Silverlight, but those should not be much complex to migrate to WPF.
On other words, you could find some things in the drops as you mentioned, since prism team could design some components for Silverlight. This is because, Silverlight codebase is subset of WPF’s one. But this
does not mean that the guidance will be more focused on Silverlight than in WPF, in the final release.
Thanks again for your feedback, since it is really valuable.
Please let me know if this helps.