Expression Blend 4 and SDK are installed. I can see the ArcGIS templates in Expression Blend, but not in VS 2010.
The API installer doesn't even give me the option to install the VS 2010 templates, so there must be some prerequisite check done by the installer that is failing. (For example, due to the fact I cannot install Silverlight Tools for VS separately because they are part of VS 2010 SP1.)