David Weller (Let's Kill Dave) posts an interesting Q&A on the XNA Team Blog.  From his blog post:

The XNA Community Games Platform team is delighted to offer you a sneak peek at our first major feature for XNA Game Studio 3.0: The ability to build games for the Zune platform!  This will let you write one game and deploy it to all three platforms that XNA Game Studio 3.0 will support: the Xbox 360, Windows, and now the Zune.   ...

Our current planning is to offer a preview release of XNA Game Studio 3.0 in the Spring 2008 timeframe, with a final release scheduled for the holiday 2008 season.  We look forward to your feedback and seeing what kind of amazing games you can create for the Zune!