Merge both frameworks to use the same assemblies and controls and make a .net silverlight profile that would be a subset of .net client profile and used by partially trusted xaps.

I have a high end PC and still WPF is not always fluent. Just compare it with QT 4.6 QML (Declarative UI) it is sooo FAST!

Requires support from the RIA Services team as well as some additional support from the Cider (WPF Designer) team

Make XAML participate in compile time syntax checking, in code refactoring (e.g. property renames), and in code navigation. Add refactoring (e.g. "Create Style from Element") and other performance features to the XAML code editor (e.g. allow in-place editing of xaml tags so that the end tag changes when you change the begin tag).

Something more like:

public observable int Foo { get; set; }

Rather than having to do all the manual event raising required by INotifyPropertyChanged

Something like where VS has a "code mode" for code behind or MVVM or other pattern.

If MVVM is selected then the IDE helps us fall into the pit of MVVM success.

Even better would be a coding mode provider model, so other patterns could be plugged in over time

Serious WPF/Silverlight development really demands that there's the ability to debug XAML, i.e. set breakpoints, step over/into XAML, examine triggers and the likes

In general, simply invest in improving the 3D framework. Specifically, add the ability (for users) to create and instantiate high level 3D elements in xaml (e.g. allow Cube, Cylinder, Sphere, etc. to be "native" WPF objects).

When we need to visualize very detailed vector graphics wpf is pretty useless. Even the basic transformations, such as pan/zoom take a lot of time (using RenderTransform or GeometryTransform).
Pure Direct3D handles it very well, and that's what I would expect from WPF (the geometry is static and frozen).

Support for a high performance line graph control based on (or similar to) the Microsoft Research Project Dynamic Data Display (http://dynamicdatadisplay.codeplex.com/). Dynamic Data DIsplay is great but work on this project appears to have stopped.

The current Webbrowser in WPF is only a wrapper around the IE WebBrowser Control. It would be great to have a native WPF Webbrowser Control.

There are new ideas introduced in WPF with x:Uid in XAML and locbaml command line tool but the translation process is a mess, see http://wpflocalization.codeplex.com/

There should also be a standalone resource editor available for translators.

Generic types etc.

Would like this both for feature parity and to provide direct support for the creation of something like a native WPF Bing Maps control. Bridging in Silverlight apps or hosting a web page are not ideal solutions

WPF Bing Map Control like in Silverlight. Include multi-touch features.

Remove the dependency on the custom Blend assembly and add Visual Studio support

Make validation accross entities easier. Something like Workflow rules engine, with dependencies between rules, dynamic loading of rules etc.